Of those mentioned already...

- Tomb Raider is a game that I think you might enjoy.
- Portal & Portal 2 are games that I think anyone who has any sense of humour and brain whatsoever will enjoy, however if you do genuinely get motion sickness through gaming then it's possibly not your best bet.
- I agree that Skyrim is far better if you play it on PC and would suggest waiting until you can do that.
- Arkham Asylum & Arkham City are really good games.
- Lost Odyssey is good but you don't strike me as a JRPG lover anymore (sadly).
- Hell yes, Mass Effect! This is the best series on the 360 as far as I can recall. Definitely reccomend.
- Deus Ex: Human Revolution is good, too. I think you'd like it alright.
- Left 4 Dead (and Left 4 Dead 2) is amazing and I actually think you'd really enjoy it. It strikes me as a very 'you' game.
- Sonic's Ultimate Genesis Collection if you like retro games, but I get the feeling that's not what you're after.

Of the games not mentioned...

- I think you would really like Far Cry 3 as both a solo and co-op experience. If you have two controllers, I'd say Far Cry 3 is about as good as it gets when it comes to co-op on the 360, at least out of the games I've played on it. And considering that includes L4D, that's saying something!

If I had to pick a few games I think you would love more than any of the others on that list, I would probably go for the L4D games, Far Cry 3 and the Arkham games.