I doubt you can find any acurate aggregate information (beyond simple case studies) on computer games used as advertisment. But if you find any good resources, then please post in this thread. I think many are interested in the subject - I certainly am.
For general information look at sites as gamasutra or npd (http://www.gamasutra.com
). For online gaming look at the number of online players of the most popular browser game websites (pogo, popcap, yahoo games ...). Find their stats and crosscheck at alexa (http://www.alexa.com
I would also look at public accounts of game publisher and resellers. If available.