Based on the Marvel comics series, but as a game it has it's own story about an alternate reality in which Apocalypse seems to have won, and destroyed the X-Men in the process.
Game Boy Advance (2001, published by Activision)
Allows for multiplayer
Characters: Wolverine(pictured above), Storm, Cyclops, and Rogue
B - strong attack
A - weak attack
forward & A when close - grab
grab, A/Away & A(depending on the character) - throw
L - super (requires the meter underneath the health bar to be turned completely blue, which fills up/turns more blue as you defeat enemies)
R - jump
R, A - jump attack
B & A - desperation
Down, Down/forward, forward & A - special
Double tap Left/Right - dash(mainly only good for closing the distance to an enemy)
Items are picked up by walking over them. In between stages, you can power up your character with points earned by beating the stage.
One of the coolest aspects is actually in the cheat code department, in particular the "Play as Character" codes you can find here http://gamehacking.org/game/6476 , which allow the player to use enemy/boss characters, which include other X-Men. Just be careful as some characters don't have some moves(mainly desperations), which will cause the game to freeze, should you try to use them.
Also, if you're emulating this one, the sound may not come in until you point the emulator to the correct BIOS file.