I think Pac-Man is more iconic, than, say, Solid Snake.
I remember Hideo Kojima's statement about Metal Gear never being on a Nintendo platform *coughMetalGear/Snake'sRevenge/GhostBabel/TwinSnakescough* which was only a few years ago yet before Twin Snakes, of course, but if it's true that he begged for Snake to be in SSB:M, well, I still think it's weird. Had he not asked, I would've thought someone more classic Konami and Nintendoish would be someone like Simon Belmont, what with his NES/Game Boy/Super NES adventures and Captain N appearance (even if that was DiC, really).

I guess Snake is more commonly popular these days, which would boost sales better than if they were going for the Castlevania fan, however, since the MGS games are coming to the PSP and PS3, it doesn't feel like a good fit.
I guess it's too late for that, though.
I think since Konami is in, then Capcom (with Mega Man) should be in. Those two were the first two third parties I recognized in the NES days that are still around and have lengthy series.
Keep your Solid Snake, stick in Sonic, Pac-Man, Mega Man, and maybe if Square-Enix ought to be there, then a moogle (or (a) Mog, whatever) and call it quits.