In case any of you have never checked out how our beloved game's core rules were analyzed at Wikipedia, here it is.
I found the Strengths and Weaknesses section particularly interesting.
Attributes
Almost all game mechanics are resolved by rolling percentile dice and comparing the results against a column of the colorful "Universal Results Table". The column used is determined by the attribute used; different tasks are resolved by reference to different attributes. All characters have seven basic attributes:
Fighting, which determines hit probability and defense against hand-to-hand attacks.
Agility, which determines hit probability and defense against ranged attacks.
Strength, which determines damage inflicted by hand-to-hand attacks as well as the success of tasks such as grappling or the lifting and breaking of heavy objects.
Endurance, which determines resistance to physical damage (e.g., poison, disease, death).
Reason, which determines the success of tasks relating to knowledge, puzzle-solving, and advanced technology.
Intuition, which determines the success of tasks relating to awareness, perception, and instinct.
Psyche, which determines the success of tasks relating to willpower, psionics, and magic.
Players sometimes refer to this set of attributes, or the game system as a whole, by the acronym "FASERIP". Attribute scores for the vast majority of characters range from 1 to 100, where normal human ability is 6, and peak (non-superheroic) human ability is 30. However, the designers minimize use of the numerical figures, instead preferring colorful adjectives in the Marvel Comics tradition, such as "Incredible" (scores from 36-45) and "Amazing" (46-62). A "Typical" (5-7) attribute has a 50% base chance for success at most tasks relating to that attribute. For example, a character with "Typical" fighting skill has a base 50% of connecting with a punch. As an attribute increases, the chance of success increases, roughly by 5% per 10 points. Thus a character with an "Amazing" (50) attribute has a 75% chance of success at tasks relating to that attribute.
Superpowers
Beyond the seven attributes, characters possessed superpowers, such as Spider-Man's wall crawling, or Mister Fantastic's elasticity. The powers function on a mostly ad hoc basis, and thus each character's description gives considerable space to a description of how his or her powers work in the game.
Each character had an origin, which put ceilings on a character's abilities and superpowers. The origins included: Altered Humans (normal people who acquired powers, such as Spider-Man or the Fantastic Four), High-Tech Wonders (normal people whose powers come from devices, e.g., Iron Man), Mutants (persons born with superpowers, such as the X-Men), Robots (created beings such as the Vision and Ultron), and Aliens (a blanket term used to cover non-humans, including extra-dimensional beings such as Thor and Hercules).
Talents
The game also featured a simple skill system, referred to as Talents. Talents had to be learned and covered a wide range of knowledges from Archery to Zoology. A Talent raised a character's ability by one rank when attempting actions related to that Talent. For example, a character uses his Agility score when attempting ranged attacks. A character with an Agility of Excellent would normally roll on that column when attacking with a rifle. However, if he had the "Guns" Talent he would treat his Agility as the next higher power rank (Remarkable). The referee was free to determine if a character would be unable to attempt an action without the appropriate Talent (such as a character with no medical background attempting to make a pill that can cure a rare disease).
Resources and Popularity
Characters also had two variable attributes: Resources and Popularity. These attributes were described using the same terms as the character's seven attributes ("Poor," "Amazing," "Unearthly," etc.). But unlike the seven physical and mental attributes which changed very slowly, if at all, Resources and Popularity could change very quickly.
The first of the variables, Resources, represented the character's wealth and ability to obtain goods or services. Rather than have the player keep track of how much money the character had in the bank or with him, the Advanced Game assumed the character had enough money coming in to cover his basic living expenses. The Resources ability was used when the character wished to purchase something out of the ordinary like a new car or house. For example, the referee might decide a character with Typical resources would probably be unable to purchase a brand new sports car, but with a Yellow Resources roll might be able to afford a used car in good condition. The game books note that a character's Resources score can change for a variety of reasons, such as winning the lottery or having a major business transaction go bad.
The second variable, Popularity, reflected how much the character was liked (or disliked) in the Marvel Universe. Popularity could be used to influence non-player characters. A superhero with a high rating, like Captain America (whose popularity is Unearthly-the highest most characters can achieve), might be able to use his Popularity to gain entrance to a club because the general population of the Marvel Universe admires him. If he were to try the same thing as his secret identity Steve Rogers (whose Popularity is only Typical), he would probably be unable to do it. Villains also had a Popularity score, which was usually negative (a bouncer might let Doctor Doom or Magneto into the aforementioned club simply out of fear). There were several ways Popularity could change. For example, if Doctor Doom defeated Spider-Man in front of the general public, Spidey's Popularity would go down for a short time. But if everyone's favorite web-slinger managed to foil one of Doctor Doom's plans and the word got out, he would enjoy a temporary Popularity boost. Since mutants were generally feared and distrusted in the Marvel Universe, these characters start with a Popularity of 0 and have a hard time improving this attribute.
Character creation
The game was intended to be played using existing Marvel characters as the heroes. The Basic and Advanced Sets both contained fairly simple systems for creating original superheroes, based on random ability rolls (a la Dungeons & Dragons). Compared to point-buy systems in other superhero role-playing games (such as Champions), the random system in MSH made it difficult to create characters based on a player's desires (though guidelines for "character modeling" were included in the Advanced Set rules). Instead, a player is given a random set of powers and makes what he can of this character.
The Ultimate Powers Book, by David Edward Martin, greatly expanded and organized the game's list of powers, making a comprehensive survey of comic book-style super-powers. Players were given a wide variety of body types, secret origins, weaknesses, and powers. The UPB gave a much greater range to characters one could create, but also allowed for potentially play-disrupting imbalances in power between characters. Additionally, the book suffered from editing problems and omissions; several errata and partial revisions were released in the pages of TSR's publication Dragon Magazine. The expanded, corrected version of the book is available for free on the Web.
Karma
The game's equivalent of experience points was Karma, a pool of points initially determined as the sum of a character's three mental attributes (Reason, Intuition, and Psyche).
The basic system allowed players to increase their chances of success at most tasks by spending points of Karma. For example, a player who wanted to make sure he would hit a villain in a critical situation could spend however many Karma points were necessary to raise the dice roll to the desired result. Additional Karma points were distributed by the referee at the end of game sessions, typically as rewards for accomplishing heroic goals, such as defeating villains, saving innocents, and foiling crimes. Conversely, Karma could be lost for unheroic actions such as fleeing from a villain, or failing to stop a crime: in fact, in a notable departure from many RPGs (but strongly in keeping with the genre), all Karma was lost if a hero killed someone or allowed someone to die.
In the Advanced Game, Karma points could also be spent to permanently increase character attributes and powers (at a relatively moderate cost, ten times the attribute number raised, powers were steeper, at twenty times the number.). The Karma system thus united two RPG mechanics–"Action" or "Hero" points (which allow players to control random outcomes) and character advancement (e.g., "experience points")–in one system. Though this system could frustrate both referees and players (the former because a player willing and able to spend Karma could effectively overcome any challenge at least once; the latter because advancement was glacially slow compared with most other RPGs), it had the virtue of emulating two central features of super-hero comics, namely, that heroes almost always win, even in highly improbable circumstances, and that heroes' power levels remain mostly static.
Game Mechanics
Marvel Super Heroes was driven by two primary game mechanics: column shifts and colored results. Both essentially influenced the difficulty of an action.
A column shift is used when a character is attempting an exceptionally hard or easy action. A column shift to the left indicates a penalty, while a shift to the right indicates a bonus. For example, Reed Richards (Mr. Fantastic) has an Intuition of Excellent, making him significantly more perceptive than the average person whose Intuition is Typical (two ranks lower). The GM might determine that spotting a trap hidden beneath a few sticks and leaves will be fairly easy, and give the player running Mr. Fantastic a +1 column shift. His Intuition will be treated as Remarkable (the next column to the right). However, a trap buried underground might be considerably harder to spot, and the GM might give the player a -1 column shift penalty. In this case, Mr. Fantastic's Intuition will only be treated as Good (the column to the left).
The column for each abililty is divided into four colors: white, green, yellow, and red. A white result is always a failure or unfavorable outcome. In most cases, getting a green result was all that was needed to succeed at a particular action. Yellow and red results usually indicated more favorable results that could knock back, stun, or even kill an opponent. However, the GM could determine that succeeding at an exceptionally hard task might require a yellow or red result.
Additional rules in the "Campaign Book" of the Basic Set, and the subsequent Advanced Set, used the same game mechanic to resolve non-violent tasks. For example, if a superhero needs to figure out how to operate a piece of alien technology, the hero would have to succeed at a Reason roll, where the chance of success is modified by the complexity of the device.
[Strengths and Weaknesses of the System
Although the Karma system gave players more control over their chances of success at dramatic moments, it also allowed frugal players to hoard Karma in order to ensure success on certain rolls, although this could be perceived as removing some of the drama from the action, it is a good emulation of the superhero genre.
Compared to superhero games like Champions and DC Heroes, a character's Agility has little impact on a character's defense. In those systems, dextrous characters enjoy a defensive bonus, much like Dexterity improves Armor Class in systems such as Dungeons & Dragons. In some game systems, agility/dexterity also influenced a character's "to hit" rolls when attacking with ranged weapons. By contrast, in MSH, Agility only influences success with ranged combat and has little effect on defense. A character must use an action and make a roll to take advantage of his or her Agility, and even then it can only be used to dodge ranged attacks.
Closer inspection of the "agility/dexterity" system reveals an altogether new paradigm over previous table top role playing games of the time which is actually a strength. The character's fighting ability in other games were either level based (such as Dungeons and Dragons) or indiscriminately consolidated into agility/dexterity. These previous systems would not accurately define a character where details such as fighting ability are distinctly different from their agility, dexterity, and speed. To illustrate a point let us compare Spider-man and Captain America. In a level based system, Spider-man's overall powers and agility would make him superior to Captain America. Captain America by experience and fighting ability would be many levels above the lesser trained Spider-man. Spider-man's superhuman agility however allows for bonuses to hit and defend. Level based systems require "hit charts". Spider-man's ability to hit and defend now modified may make him more potent than Captain America. In the HERO based system such as Champions, there is no distinction between Dexterity and Fighting ability other than skills. In Marvel Superheroes, action is central to character definition. Raw fighting ability (offense and defense) is well defined within the entire scope of the abilities of Fighting, Agility, and Strength and modified by Talents as appropriate instead of relying on arbitrary levels and armor class statistics. Each fighting style is categorized under a base ability. Raw fighting skill and Evading is defined by the FIGHTING ability. Ranged attacks and Dodging is defined by AGILITY. Grappling and Throws are defined by STRENGTH. So applying this to MSH, Spider-man is not as seasoned a fighter as Captain America and rates a Remarkable(30) raw fighting ability with an Amazing(50) agility ability. Captain America on the other hand is a decades-seasoned combatant with Amazing(50) fighting ability and only Remarkable(30) enhanced agility. Needless to say we won't see Captain America performing supernatural acrobatic feats on tightwires like we would see Spider-man, but he would still perform better in raw combat ability and knowledge. The dexterity/agility model system does not inherently make character distinctions in abilities as clearly as the Marvel Superheroes' FASERIP system.
MSH also introduced to superhero gaming the concept of the "Power Stunt"–the use of a particular power in a way that goes beyond the bounds of its rules-defined limits. This was an innovation over previous popular superhero games such as Champions, and the concept has been incorporated into subsequent superhero games.
The "one-chart" mechanical format enjoyed a vogue in mid-eighties roleplaying games, before the advent of more abstract, largely chartless mechanics made popular by White Wolf Games in the early nineties. While the format has its limitations, it does make for quick and simple resolution, greatly speeding gameplay, which is arguably a vital element in a game meant to simulate the genre of mainstream superhero comics. Although the older Champions game, based on the HERO system, has remained more popular over the years, it is generally held to be more complicated and somewhat less conducive to a "quick and dirty" playing style.