Considering the characters in the first game (Oracle, Hush and others) this is a fairly recent version of Batman. Tim Drake will almost certainly be Robin in AA2.
If your disagreement is that we shouldn't have to BUY them, I'm with you--it should be free. Alternate outfits add much-needed spice to fighting games. No one wants to see their favorite character in the same tired outfit time after time...after time.
I agree that Metroid looks good, but how is it that you don't consider it a sequel? Sure, it isn't Prime 4, but it's still a follow up to an established Nintendo character.
Also, although it wasn't a GREAT game, Castlevania: Lament of Innocence was pretty fun.
He's not well known (yet), but Rufus is not only the fattest character in Street Fighter IV, he's also the fastest. Getting beat down by fatties is humiliating even in the digital realm.
There's also Chang (KOF), Cheng (Fatal Fury), Earthquake (Samurai Shodown) and a bunch of others who can floor you if you don't watch it.
King's Illusion Kick super from KOF '94 and Ukyo's Bust super from Samurai Shodown III are the best special moves ever. Ryu Hayabusa's Izuna Drop is a close third.