Simon should've definately been in the game. Have him, Mega Man, and Pit, and you've got a good chunk of the Captain N team. Not to say that's the biggest reason, but they all were pretty notable characters back in the NES golden age. Probably up there in nostalgia with Mario and Link.
Little Mac should've been a fighter!!
As for Cloud, he's been Square's posterboy for Sony. Doubt he'd be included in SSB. I don't think he's ever appeared in an Nintendo SE title. All the others, I've listed, HAVE. Solid Snake, if you forget his Metal Gear Solid role, will always fall back on the ORIGINAL Metal Gear, which of course was NES. Cloud, I'm not sure.
I really would've loved to see some other old VG characters appear:
- Kuros(Wizards & Warriors)
- Mappy(Mappyland)
- Lolo(Adventures of Lolo/Eggerland)
- Karnov(Karnov)
- Bub and Bob(Bubble Bobble)
- Peter Pepper(Burgertime)
- Billy Lee(Double Dragon)
- Mikey(Goonies 2)
- Kid Niki(Kid Niki)
- Nemo(Little Nemo the Dream Master)
- Milon(Milon's Secret Castle)
- Bomb Jack(Mighty Bomb Jack)
- Twinbee(Stinger/Twinbee)
- Big Bang(Clash at Demonhead)
- Ryu Hayabusa(Ninja Gaiden)