A repost of mine from somewhere else:
Definition of a Fighting Game
I’m not sure if you can create one all encompassing definition for the term “fighting game”. At best, I think a “fighting game” is a just a collection of certain traits. I think you have some core traits, and then a large number of optional traits built on top of those.
CORE TRAITS
The only core traits that are truly core to a fighting game is one player, controlling [an] avatar[s] beating up some other guy’s avatar[s] in an enclosed screen/space. This “other guy” could be another player or CPU (SF2 without 2 player would still be a fighting game, just nowhere near as fun).
This is still a very broad definition. Let’s go into further detail.
One player Vs. Something
The player is pitting his will against some other entity, be it another player or against the CPU. The player must control an avatar of some sort that represents him, and not just some abstract entity. The player can control multiple avatars vs. another opponent’s multiple avatars (i.e. in team-based fighters like KoF or Vs. games), but typically the player only has direct control over one avatar at a time. Even in MvC2, the only true 3 on 3 based fighter, the player mainly controls one character (3 player glitch notwithstanding), with the others being relegated to a single solitary actions and do not operate independently of the player.
Beating up the other guy
One player is engaging in some sort of contest against another player. This refers fundamentally to physical combat between the avatars, i.e. punches, kicks, throws, etc. This includes projectiles, of course, which are really just extensions of physical combat. This is arguably the most basic trait of fighter: You can’t have a fighting game without actual fighting in it somewhere along the way!
Enclosed Screen/Space
The enclosed space means that it’s not possible for the avatars to lose track each other. Each player is aware of where the other player’s avatar is at all times. Even in the case where the opponent isn’t immediately in view/reach, such as Storm flying off the top of the screen in XSF or in those DBZ fighters were the players can go FAR away from each other with a split screen effect, you’re always aware of where your opponent is.
To summarize, the three broad traits of a fighting game include:
1) One controlling avatar/set of avatars vs. another entity's avatar/set of avatars.
2) Victory primarily involves one player beating the other player up through fighting.
3) Avatars must engage in an enclosed space such that both players are aware of each other at all times.
NON-TRADITIONAL FIGHTERS
Non-Traditional Fighters are games that have many/most of the basic tenets of traditional fighters, but also have unique properties, possibly borrowed from other genres, that make it difficult, if not impossible, to lump them with the more standard fighters. The most famous example of this, of course, is Super Smash Bros.
Super Smash Bros. is definitely a fighting game. In fact, if you do a breakdown analysis of its features (items, changing stages, stage hazards, etc.), you will find 99% of them can be found in other traditional fighting games. One of these days I’m going to do just that. It’s just that having all of these features at once in the same game makes Super Smash Bros. very unorthodox.
Underneath it all, the two key traits that separate Smash Bros. from its more traditional brethren are its multi-player nature and its Percentage system. The multi-player aspect can be neutralized merely by sticking to 1 on 1, as they do in tournaments (it’s still a fighting game with more players; just that reducing it to standard 1 on 1 helps reveal its basic nature better; if you played 1 on 1 in, say, Halo, though, it wouldn’t suddenly turn Halo into a fighting game). That leaves the percentage system. The percentage system is actually a combination of a traditional life bar system and a variable gravity system, both of which can be found in traditional fighters, so it’s really not that alien.
HYBRID FIGHTERS
Some games incorporate many of the important elements of fighters and merge them with other genres, sufficient to label them as hybrid fighters depending on how much of each genre they incorporate. A key example of this is Senko no Ronde, which is a bizarre shooter/fighter hybrid. It’s 1 on 1 and it has an enclosed space, but the fighting takes the form of two ships shooting at each other, which makes it more shooter than fighter, but it still has enough recognizable elements of a fighter that the hybrid label is justified.
RELATED GENRES
There are some genres that are related to fighting games that people seem confused as to how they stand in the grand scheme of things. These are as follows:
Wrestling/Boxing games
Wrestling games and boxing games can safely be considered fighting games. I don’t know why this is a problem. Hell, originally, Street Fighter 2 itself was described as a cross between a wrestling game and a martial arts game.
Beat 'em Ups
Beat 'em ups are actually the original fighting games. Before Street Fighter 2 and its clones/follow ups monopolized the term, games like Double Dragon and Final Fight were called “fighting games” because the central premise to these games was, well, fighting. You could say 1 on 1 fighters are a subset of beat 'em ups, the “true” fighting game genre. This is certainly true, but as it is now, because of the sheer dominance of 1 on 1 fighters and the near total lack of their predecessors (Dynasty Warriors notwithstanding), beat 'em ups are considered a closely-related but separate class to what we refer to as “fighting games”, i.e. the more 1 on 1 [or rather, X on X] variety. It may not be correct, but that’s the way I see things at this point.