I think that there are too many "beautiful" game apps (3D, for example).
Simple and multiplayer games could have success (but I could be wrong, of course).
Also...
An italian member has two apps:
1) a word game (italian only, unfortunately);
2) an app with simple phrases of love (again, in italian).
Well, the second one obtains more downloads (about 10 times!).
An app for female (stupid) teenagers could have success: if you could talk about One Direction, with some of their photographs, your app would get millions of downloads, for example.