that 8 player x-men game was my allll time favorite. it was so insane at my arcade b-day parties cuz 8 of us would all be playing and it was chaos. I loved all the x-men fighter games, marvel vs. capcom 2 being my favorite, but childrne of the atom and xmen vs street fighter was great, so was war of the gems and dont forget Marvel vs Street fighter which had different guys than xmen vs street fighter with some similarities, and marvel vs capcom 2 obviously being the culmination of most if not ALL of the characters from xmen:children of the atom, marvel super heroes, xmen vs. street fighter, marvel vs. street fighter, and marvel vs capcom.
I only talk about it now cuz at work (game crazy) i play my copy of MvC2 for PS2 like every single shift, it's just too fun. Kind of sucks though cuz the game is rare so customers see me playing it but can't get it in store, i've only ever seen 1 more copy traded in and it was just the game, no case or anything.
But I loved them all from childrne of the atom to MvC2, I've played them all, have tons of fond memories of me and my friend at an arcade in New hampshire when we went to his family's trailer up there in the summer (we live in RI) and there's an old arcade and we spent tons of money trying to beat damn Magneto but he always flew in the air making it harder to get at him. The bastard.
EDIT: Don't forget, for PS2 the Street Fighter Alpha anthology comes out, it has Street fighter alpha, alpha 2, alpha 2 gold, and alpha 3, PLUS Gem fighter mini mix (Puzzle fighter) all in 1 for $30, comes out tomorrow. I for one cannot wait cuz I loved those games too.