I haven't delved into the arcade all that much...but Hexic is fun. I have other xbl friends that like to play Feeding Frenzy.
Also, there is a new game on there called 1 vs. 100 that is free (at this time it's in beta testing mode). It's modeled after the game show on TV and it is general trivia. I think you would like it. They have live shows on the weekends, and all the other times it's on is extended play, which gives you a better chance of qualifying to be in the mob or the 1.
Hmm, I didn't know SOTN was available. I've played Circle of the Moon and Aria of Sorrow and liked them both, I should give it a shot when I'm tired of blowing up half of Mars with hydrogen tanks and my blade-shooting supergun.
Also, Ikagaru would be good if I want to develop Carpal Tunnel. Hmmm.