I am up to about 20 XBLA games
My favorite is Catan. But I also love the puzzle type game Hexic 1 and 2, Lumine Lives, Jewel Quest and as weird as it seems Soltrio Solitaire. (playing solitaire on a powerful machine like the 360
)
I can't say I am not happy with any game I bought because of demo. But the top of this category would be New Rally-x
But one game I use to enjoy, but I am having problem is UNO. The game is classic, nice and easy, but it is becoming impossible to play on-line. Most of the time I find guys who only wait to catch boobs on the camera!!! ... I like boobs, but not necessary to see them on my 360