X-Men is a multi-screen 6-player brawler from Konami that's based off the Marvel Comics series. It features Wolverine, Storm, Colossus, Nightcrawler, Cyclops, and Dazzler as playable characters although more characters are available as special attacks.
Certain versions of X-Men feature a whopping 6 simultaneous players on two screens. There are also 4-player and 2-player versions as well, both of which use a single screen.
X-Men is also available on PSN and Xbox Live.
X-Men was definitely made by Konami at the top of their game. Its phenomenal sprites capture the style of the animated show flawlessly and the funk-tastic music sets the tone for pure fun. It's combat is super simple although it does have ground attacks which liven things up quite a bit. It's not that hard, though.