The 360 is magic. I love it. I actually suggest going through XBLA and picking up some fun stuff there, I only even ever play "real" games about half the time on it because XBLA games are so cheap and easy and fun to download.
Assault Heroes I and II are awesome timewasters...at one point I was #10 on Normal on the leaderboards and #7 on Hard.
Geometry Wars Advanced or whatever it's called on the 360 is very popular and fun too (I didn't buy it, but it's good stuff).
What else...Soul Calibur IV is spectacular...Ninja Gaiden II as well.
And you might even want to take a look at XNA, you being a programmer of no small skill. I can't describe how cool it is to see your own creation showing up on a console. If you sign up for Dream-Build-Play you don't actually have to submit anything and they'll give you a six-month Creator's Club subscription for free.
Some of the Community Games are cool too, there's a lot of crap, but if you sift through it's kind of like the modern-age equivalent of the old shareware bins for your 386 or whatever.
Takes me right back, I love quirky indie stuff.
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In other news, what am I playing? I am double-fisting House of the Dead 2 & 3 Return! I love it!
Used to put in two bucks and play with two guns in the arcade and now it's free. I get to pretend I'm Chow Yun Fat.