Bought an iPod Touch for my son which I then discovered is a 2nd gen which doesn't support lots of apps and games. Currently I either have to try downloading a game to see if it fails or read the blurb for each one, which is a complete pain in the ass. Is there any way to sort or filter iTunes so that the only results I see are the ones which will actually work on 4.2.1?
First I would try upgrading the iOS if possible. From limited research it seems that some games are requiring 4.3. I don't know if your iPod will work with 4.3.
Here is a limited list of compatible games I found http://forums.toucharcade.com/showthread.php?t=153098