Originally Posted by
Elusive
You made a mistake in your post; I've fixed that up for you.
Stand-out single-player 360 games? I really enjoyed Bayonetta and Burnout Paradise - they're both focused on silly, OTT action in their respective genres, but they're sleek, well-presented, have fantastic controls, and basically are joys to play. Dead Rising is a gigantic love-letter to zombie movies, but it's an early title and it shows. Halo is a fun shooter with plot for window decoration. Mass Effect is science-fiction RPG, and a love-letter to Star Trek, Star Wars, Battlestar Galactica, and any other space opera series you could name.
[edit] Dead Space is a great horror game, too. It's Alien meets Resident Evil meets Dawn of the Dead, but it's a fantastically scary game.
Really, there's lots of demos up on the Marketplace. I'd just pick a genre, set them downloading overnight and have a browse at your leisure later.