I have seen your build on a previous thread. You're choice of games will be limited due to the low power of your CPU and GPU unfortunately. Also asking us what are the best games ever is difficult, what genre of games do you prefer?
Also try using this software: 3d Analyzer
Don't listen to anybody who tells you that it doesn't work!!
I've personally used it and successfully played a few games at a playable fps (25+) on my GMA945 onboard graphics before I got a discrete graphic card.
Although you should remember that this software is NOT a replacement for a discrete graphics.
Games that I've successfully played using 3d Analyzer:
Splinter Cell Chaos theory
Prince of Persia SOT
Far Cry 1
Left for Dead 1&2