mecht, id say as a owner of a psp for well since its release, for gaming... its a complete waist of my money, Monster Hunter 1 and 2 are the only real games that have ANY kind of playability the rest are short, crap or just plain bland, especially Crisis core which i found to be a utter bismal of a game (but ofcourse it was gonna be its a spin off and Final Fantasy has become crap) Well after 10 that is.
Personally, for sheer cheapness, funzies and overall beasting-ness id say DS is probably better
next and only decent game for PSP i would say is Final Fantasy Dissidia (FF Beat em up style game like DBZ Tenkaichi)
DS, has final fantasy 1-4 (3 and 4 being redone in 3d) which may i add where done EXACTLY the same as their 2d counterparts but with much better graphics (cant go wrong there can you) World Ends With You (another Square game) rather fast tricky to get a hang of, but by christ is there alot of ability's / skills, then we have good old Disgea DS (probably one of the best if not thee best Tactics RPG i have played ever next to Flame Emblem which again is also on the DS)
and heck to be honest, my list just goes on and on, Mana Series, Final Fantasy 1-6 being re released, Chrono's being brought onto it. EVEN Ragnarok online is getting ported onto it.