I've never played any Assassin's Creed games, but from what I understand they have character-driven plots that expect the player to care about their characters and the world around them. Giving the player some customization options could potentially help this. I don't think having an established character is necessarily a bad thing if done well, but if customization is such an important thing to your friend I can understand his reasoning.
Brawl, on the other hand, is a party game in which you have fun beating up a bunch of iconic characters controlled by your friends. There is no plot because the insanity of the gameplay would defy even the best writer. There is no customization because the entire point is that you already know who the characters are. Emotional connection comes from nostalgia, not player involvement.
So, no, I don't think your friend is a hypocrite at all. I do, however, look askance at you for bringing such a trivial conflict to the Escapist looking for validation of your own view.