How do you know that? We've never had Smash Brothers on a handheld so you can't say if it would work or not. I think you'll find that fighters are quite good choices for handheld games. Add multiplayer Wifi and I'm sold. I have to admit that Nintendo is rather stupid for not putting this game on DS. Either they don't have a clue about how good of a game it could be, or they don't care and wipe their asses with million dollar bills (the more likely). It wouldn't be to hard to do either. Outstanding though the SSB series is, it's not that complicated of a game. It's not like the next-gen Mario game or Final Fantasy that has to stay in development for years and get reworked and tweaked. Still, there's Bleach. Has anyone tried Bleach? Does it have similar gameplay to SSB?
We can still hope for this under a different company. Nintendo hired Camelot (Golden Sun developers) to make the GBA Mario Tennis and Golf games. Maybe they'll get a third party company to publish SSBDS.