I see your point but i just said 5 becouse why the psps library isnt nearly as big as dses. The ds has like 3 times the games psp has.
I would argue there are actually more top quality titles for PSP than for DS, total library count be damned. Here's my list:
Crisis Core: Final Fantasy
Half-Minute Hero
Patapon 1 & 2
Castlevania X Chronicles
Metal Gear Portable Ops & Portable Ops +
Final Fantasy Tactics: The War of the Lions
God of War: Chains of Olympus
GTA: Vice City Stories
Mega Man Maverick Hunter X
Mega Man Powered Up
Half-Minute Hero is probably my favourite. Honourable mentions go to Crush and Dissidia Final Fantasy, and Metal Gear Peace Walker and Persona 3 Portable will undoubtedly make the list when they come out.