Each in their own category of course. Both have decent libraries so far, but nothing really amazing size-wise. Based off of what I own, I'd have to say...
DS:
1. New Super Mario Bros.
2. Animal Crossing: Wild World
3. Mario Kart DS
PSP:
1. Metal Gear Ac!d
2. Wipeout Pure
3. Have no third game, >_>.
DS:
1. New Super Mario Bros.
2. Animal Crossing: Wild World
3. Mario Kart DS
PSP:
1. Metal Gear Ac!d
2. Wipeout Pure
3. Have no third game, >_>.