Honestly, I'd just like to see Palutena, Pac Man, and Snake just to appear throughout the whole thing. I would've said Mii's, but let's just say my opinion has changed on them over time.... but yeah, Snake and Pac Man will especially make me happy, since we're talking gaming legends here:
Mario: Sidescrolling legend, brought video games back after that gaming crash....
Link: RPG Legend, games are some of the best of all time
Sonic: Another sidescrolling legend, super fast, Sega (once Nintendo's rival)'s mascot, represents the age of the 16-bit
Mega Man: ANOTHER side-scrolling legend, flourished the entire side-scrolling shooter genre
Snake: Revolutionized the stealth genre, very innovative and brought forth tons of clones that try to replicate Metal Gear's formula
Pac Man: Arcade legend, most recognized video game character of all time. You can't go wrong with that.
Color Game TV: Although an assist trophy, it's Pong. THE FIRST VIDEO GAME EVER MADE!!!!!
You see how epic this game could be? It could practically be the pinnacle of all games, displaying gaming's top moments as well as an interesting and unique fighting system that not a single game has been able to replicate. To top that off, you can play it competitively on the go, or at home, in 3D or in HD. That's why I'm hopeful to see Pac Man and Snake for E3. People will go nuts until it releases. No. Scratch that. They'll go nuts for years. Anyways, yeah, sorry for my essay XD I kind of go into a phase every time I start getting worked up about Snake and Pac Man