XBL Friends Finder

Get connected : XBL Friends Finder:

To help you find new friends that have the same games as you do, the XBOX Live Friends Finder can provide you with a list of gamertags that best match the games you have played and gamerscore achieved. It uses data from 360voice.com so you'll need to register there as well.

Here is an example match the service found for me:

You and mercillesgrunt seem to share 4 games: Call of Duty 2, Hexic HD, Outpost Kaloki X, and G.R.A.W.. Two of his favorite games are MLB 2K6 and Call of Duty 2.
Your gamerscore is very similar as you see!

I'd say the probability of you and mercillesgrunt to play well toghether is 62%
You can make a try, who can tell.