X-Men vs. Street Fighter

X-Men vs. Street Fighter (エックスメンＶＳ．ストリートファイター) is a Fighting game originally released as a coin-operated arcade game in. It is Capcom's third fighting game to feature Marvel Comics characters and the first game to match them against their own, with characters from Marvel's X-Men franchise being matched against the cast from the Street Fighter series.

It was the first game to blend a tag team style of combat with the Street Fighter gameplay, as well as incorporating elements from Capcom's previous Marvel-themed fighting games, X-Men: Children of the Atom and Marvel Super Heroes. It was ported to the Sega Saturn in 1997 and PlayStation in 1998. However, the tag team feature was omitted from the PlayStation version due to memory limitations.

Plot
During his travels, Ryu crosses paths with Cyclops and the X-Men, who show interest in Ryu's power. When Apocalypse appears, stronger than ever before, Ryu's friends and the X-Men band together to combat Apocalypse, some for the purpose of saving the world, and some for their own evil agendas.

Gameplay
X-Men vs. Street Fighter uses a system similar to the style developed in Marvel Super Heroes, and adds the tag team gameplay feature. Instead of the usual best-two-out-of-three round format, the game's matches consist of two-on-two battles between tag teams. The player controls one character at a time, while the other awaits off-screen. The starting character can tag the waiting one in at any time by hitting the Hard Punch and Hard Kick buttons, which activates the "Variable Attack"; the tag partner will jump in with an attack and taunt briefly. During their taunt, they are vulnerable to counterattack. The dormant character will able to recover a portion of their vitality, while the current character is fighting. If one character loses all of their vitality, then the tag partner will automatically come to play. A match is over when both members of a team are defeated or if the timer on the match clock reaches zero.

There are other ways to bring the character's partner in; the "Variable Counter", which replaces the Infinity Counter of Marvel Super Heroes, breaks the player's guard to bring the teammate in with a counterattack at the cost of a level of super meter. Also, the "Variable Combination" is a two-character Hyper Combo (the super moves featured in the game) which costs two levels, and will switch the player's current character as long as neither character gets hit during their Hyper Combos.

The X-Men characters come largely unchanged from X-Men: Children of the Atom and Marvel Super Heroes, and three characters new to the series are introduced in the form of Rogue, Gambit and Sabretooth. The Street Fighter characters use their Street Fighter Alpha 2 forms and their special moves were given upgrades to match the larger-than-life atmosphere of the Marvel games (for example, Ryu's Hadouken is much larger than it is in other games). This game marks the first appearance of "Shadaloo" depiction of Cammy, who would reappear in the console versions of Street Fighter Alpha 2 Gold, as well as in Street Fighter Alpha 3.

Characters
Apocalypse is the final boss of the game and lacks a tag partner. After defeating him, the character that defeated Apocalypse is forced to fight his or her teammate (the game will not accept new challengers at this time). Once the CPU-controlled teammate is defeated, the game will show the player-controlled character's ending.

Reception
The arcade version of X-Men vs. Street Fighter was met with a widely positive response. It streamlined the style and introduced the concepts of the Vs. series. In 2010, UGO.com listed X-Men vs. Street Fighter among the top 25 fighting games of all time, stating: "XSF got a shameful home port, but if you happen to spot it at one of your finer neighborhood arcades, surrender your quarters at once.". That same year, FHM included it on their list of five "coolest" video game crossover ever.

The PlayStation port of the game received a mixed to negative response by press and fans alike, earning a "passable" 6.0 at IGN and a "bad" 3.6 at GameSpot. Due to RAM limitations of the PlayStation, this port was significantly inferior to the arcade in both graphics and gameplay. A lot of frames and sprites were removed(making the game look awkward and choppy), performance was still unacceptable with slowdowns during special moves that made the game essentially unplayable, and also the tag-team setup was not included; instead, it used a traditional best-two-of-three round setup in a similar manner to Rival Schools: United By Fate. It was possible to have a tag-team match through two-player "Crossover Mode", provided that each player uses a clone of their opponent as their partner. For example, if the player is controlling Ryu and his opponent is Wolverine, then the player's partner will be Wolverine and the opponent's partner will be Ryu.

The Sega Saturn version received much better reviews, getting a 7.4 "good" review at GameSpot. The Saturn version makes use of Sega's 4MB RAM expansion cartridge (which came packaged with the game) to retain all the frames, sprites, and the tag-team setup, thus making this version arcade perfect. This version also features faster loading times. However, the Saturn version was available in Japan only. Sega Europe intended to release the game in Europe bundled with the expansion cartridge, but their plans were eventually shelved.

Legacy
The game started the trend of Capcom's multi-franchise crossover games, being followed by Marvel Super Heroes vs. Street Fighter, SNK vs. Capcom and others.