I feel in some respects it'll outperform Brawl rather handily (online I seriously hope, single player modes, overall game feel if the single match we saw was indicative of what's to come), but it's really hard to say otherwise when it comes to metagame, character design, and stages (and I sincerely hope items are better than Brawl's or at least Pokeballs are less terrible). I always had some kind of dream of a Smash game introducing a type of mini-game that's insanely addicting and fun that operates within the game's system itself, but without the direct goal of beating the tar out of each other. Something that really ramps up party play without technically using the same premise as the other modes do.
Samus ruined Metroid forever. She keeps killing them. ~CTsChoco