-The Adventure mode (Subspace Emissary) gets really repetitive really quickly, but the animated cutscenes in between are fantastic. Normally I don't like too many cutscenes in games, but these are just awesome (especially Donkey/ Diddy Kong's entrances).
-Snake. Doesn't need to be in there. He looks out of place, he feels out of place, and his move set sucks (except his Final Smash move, which is arguably the best out of all the characters).
-The Masterpieces (the little game demos in the Vault) feel kind of pointless. The demo of Kid Icarus is ridiculously short. Instead of having a timer, they should have just made it so that you could play until the end of a level.
Other than that, I really can't think of anything. This game is a must-own. I'd give it a 9.5/10