Well, I'm mixing it with both First Class and Ultimate X-Men.
Thomas Dekker as Scott Summers/Cyclops
Olivia Thirbly as Jean Grey/Marvel Girl
Alex Pettyfer as Warren Washington III/Angel
Nicholas d' Agosto as Henry McCoy/Beast
Katerina Graham as Ororo Munroe/Storm
Okay this choice depends on either you want a more serious Iceman (Hutcherson)
Or a more Comedic Iceman (Levy).
Josh Hutcherson as Bobby Drake/Iceman
Matthew Levy as Bobby Drake/Iceman
Kellen Lutz as Piotr Rasputin/Colossus
Alexander Ludwig as Alexander Summers/Havok
Eliza Bennent as Lorna Dane/Polaris
Kevin Spacey as Professor. Charles Xavier
Clive Owen as Erik Lehnsherr/Magneto
Elijah Wood as Mortimer Toynbee/Toad
Lydsey Fonseca as Rogue
Ryan Hansen as Pietro Maximoff/QuickSilver
Ashley Greene as Wanda Maximoff/Scarlet Witch
Michael Rooker as Frederick J. Dukes/Blob
James Mcavoy as Jason Wyngarde/Mastermind
David Zayas as Dominikos Ioannis Petrakis/Avalanche