For X-Men 4
Sentinels
Magneto, Quicksilver, Scarlet Witch, Juggernaut, Pyro, Avalanche
Mystique, Havoc, Sabertooth, Multiple Man, Forge
Professor X, Wolverine, Storm, Beast, Iceman, Shadowcat, Colossus, Nightcrawler, Angel, Rogue, Gambit
Wow! Seeing somebody else with a cast as big as mine makes me feel a lot better! XD Mine is:
Sentinels, Steven Lang (dies), Bolivar Trask
Magneto, Mystique, Pyro, Avalanche (dies), Scarlet Witch, Quicksilver, Tempo (dies)
Storm, Wolverine, Beast, Iceman, Shadowcat, Angel, Nightcrawler, Rogue, Colossus, Gambit, Illyana Rasputin (student, minor role)
I have 20. Not a lot less, I guess. Still makes me feel better about my cast, though. ^^
For X-Men 5
Sinister
The Hellfire Club
Phoenix
Professor X, Cyclops, Wolverine, Beast, Iceman, Shadowcat, Nightcrawler, Angle, Rogue, Gambit, Psylock, Havoc, Forge
For X-Men 6
Apocalypse
The Four Horsemen
Professor X, Cyclops, Jean Grey/Phoenix, Wolverine, Beast, Iceman, Rogue, Gambit, Psylock, Havoc, Forge, Angel/Archangel
My scripts don't call for an X6 - only X4 and X5. X5's major storylines would be Apocalypse and the Legacy Virus, which begins as a deadly side effect of the ineffective "cure" but becomes contagious to all mutants. My cast would be a lot bigger than the previous one, but several characters would get sidelined or killed by the Legacy Virus. I haven't written it yet, but here's the working cast:
Sinister, Apocalypse, Sunfire (Famine), Wolverine (War, lured to the dark side by Sinister), Archangel (Death, lured to the dark side by Sinister) (Pestilence, I have no idea which mutant to use) --(whole team dies)--
Magneto, Mystique (sidelined, but recovers, dies in battle), Pyro (dies from virus), Scarlet Witch, Quicksilver
Storm, Beast, Iceman, Shadowcat (dies in battle), Nightcrawler (sidelined, but recovers, dies in battle), Rogue, Colossus (dies to activate the legacy cure), Gambit, Illyana Rasputin (dies from virus), Moira, Phoenix (Sinister revives her, but she escapes him), Cyclops (Phoenix revives him from a comatose state in Sinister's lab)
Again, it's a working idea. I'm sure some things will change.