I would agree it is probably best to clear the cache on your console, instructions on how to do this are here : http://support.microsoft.com/kb/971755

Can't believe they've only got one mention thus far but the GTA games for me. They expand on the console based games and the new Chinatown wars moves beyond that and the 100+ hours you could possibly get out of those three are probably worth it alone.

I picked them all up with my second PSP (purchased last month) for less than £20.