FF XIII takes the big bang, but I'm definitely interested in the "New Xbox Experience". Avatars give us something else that our achievements can work towards fleshing out. The avatars are simple enough to where they could be implemented into arcade game, and I hope they don't just waste time doing such a thing with game shows and casual things, but also allow us to maybe use them in something like a brawler or something.
Hardcore shooter fans have taken true gaming passion into "Cute em Ups" like Parodious for years, so I see no reason why Avatars can't be a solid creation for Hardcore gamers too, if used right. It's like merging the Dashboard with the DOA4 online avatars. Imagine how interesting it would be to unlock a Chibi Kaim from Lost Odyssey, or a Pocket/Puzzle Fighter-style Ryu along with Street Fighter 4?
I always thought Miis where a missed opportunity. When I first saw then, I was hoping to see the simple characters get upscaled and imported into full games, taking the simple features, and making more complex characters based off their rudimentary shapes. So, say, importing your Mii into a Phantasy Star Universe style character creator, and playing the character in a game.
That hasn't panned out yet, so I'm intrigued in seeing if they can pull something like that off with 360!