My two cents: SmashU needs more HOO HAH.
Why? It's stupid and pointless, obnoxious as hell, and it emphasizes a relatively boring and simple combo over all of the game's depth and strategy. What's the big deal?
Well, go back and watch the Wombo Combo. Don't bother watching what's happening in the game; just listen to what people are saying. It's ****ing insipid. I mean, what the hell is even the relationship between anything that's said? "My **** hurts!"? What are we? 13? Wombo Combo is a really friggin' stupid thing, and then when you watch the combo without audio, it's hard to tell what people are even getting all atwitter about. It's a pretty standard grab-lock team combo. It's not particularly difficult, up until the reaction knee at the end.
But that the Wombo Combo is a watershed moment for Melee is not even a matter up for debate at this point. It showed the world not what Melee was at its most sublime, but what it meant to the people who loved it. It makes them giddy, it makes them incoherent and bug-eyed, even for the little things. Three months later, the first RoM was meant to be a last hurrah for a dead game, but that's when it became apparent that people were still paying attention. But it wasn't because the game was good, it was because it was clear there was a community that loved this game and embraced it, flaws and all (regardless of whether you think Melee's good or not, this statement holds). Wombo Combo was pivotal in establishing that love.
HOO HAH! is a phenomenon. Full disclosure, I am something of a Melee Elitist. I have a pretty strong opinion that, all told, Melee is a better game, and I honestly have a difficult time sitting through most SmashU games. That's not really here nor there. When I watch a Diddy Kong match, watching for the grab so I can shout, "HOO! HAH!" keeps me engaged, and I enjoy the entire match, regardless of how long it takes. Shouting like that, I can feel at least a comprehension of the love a SmashU player should feel for the game. It's through this kind of participatory, unqualified adulation for the game, that people who do not understand the game come to appreciate it. And with that, viewer base will grow, and with a larger viewer base, a larger player base will come.
Max is right. You need to love this game, and show it. If SmashU fails, it won't be because Melee elitists like myself killed it. That gives us waaaaay too much credit (and to tell you the truth, there are many such people who would be all too happy to believe it if that's what you said). What will kill it is if you don't love the game, more importantly if you don't love the parts of the game that are stupid and broken, and if you don't love those parts more than the parts that play as intended. What will kill it is if we can tell you don't love the game. So love it. And convince the world you love it. But above all, in the words of President Snow, "convince me."
And for Celestia's sake if there's a character as broken as Metaknight, just ban him now. (Diddy's not that broken.)