For example, I want to buy Portal 2. When I look up Portal 2 on Steam, it tells me which of my friends already own it, which is tremendously helpful. As far as I can tell, there's no easy way to do that on Xbox.com.
I've noticed that you can see game activity by going to http://live.xbox.com/en-US/Activity/Details?titleId=xxxxxxxxxx where the Xs represent a title ID. There isn't any easy way to look that title ID up either. Here is the link to Portal 2: https://live.xbox.com/en-US/Activity/Details?titleId=1161890066. I can't seem to go there unless I own the game, which kind of defeats the purpose. Even weirder: When I am on the Social page on Xbox.com I can see my friends' activity and click on a game I don't own to see who does own it. That's exactly what I want to accomplish but it only seems to work with games popular enough to make that list.
I feel like this may need a custom-coded solution (maybe a Chrome add-in or a Greasemonkey script) and unfortunately it'd be pretty far down on my to-do list. Does anyone else have any ideas?