I'm currently running a small mobile game startup (about 3 people). We spend a lot of money buying apps from the Apple app store and Google Market to check out what sort of games are out there. What sort of category would these purchases go under in "Chart of Accounts"? Would this be considered R&D?
Yes you correct - Log it under an expense named 'R&D'.
It's an expense of course - we can't consider these purchases as assets because you don't intend to sell them. Even if you did the app stores wouldn't allow you to by their license or terms of service agreement. (See Apple's conditions under the heading "Licensed Application End User License Agreement")