I can't tell you whether or not those games I mentioned are good or not, but that's why I mentioned the developers. I personally can't think of a bad Level 5 game, and b/c of the Professor Layton series, they're quite popular in Japan. Square is another company that usually releases solid games, especially if Yoshinori Kitase is involved. So going off reputation, these are probably pretty solid titles inspite of which didn't sell well on a system with a huge install base. This is why you still see a sparse few developers throwing quite a bit of support at the PSP (Square Enix comes to mind).
My Top 5:
Shadow of the Colossus, Metal Gear Solid 3, Shenmue, Skies of Arcadia, Chrono Trigger
My 2 nex-gen systems: PS3 
and Wii 
Prediction Aug '08: We see the PSP2 released fall '09. Graphically, it's basically the same as the current system. UMD drive ditched and replaced by 4-8gb on board flash memory. Other upgrades: 2nd analog nub, touchscreen, blutooth, motion sensor. Design: Flip-style or slider. Size: Think Iphone. Cost: $199. Will be profitable on day 1.
