Often I can find info on games at
MobyGames. If you sign up and bother to submit good, well-researched information you can help add games to the system. They're picky, but that helps make the information (somewhat) more reliable.
Do note that there are obviously holes where stuff needs to be filled in. Last I checked Ace Combat X (PSP) and the entire Bit Generations line (GBA) weren't in the system.