I guess it just depends more on how many games you need for it to be "worth it". I pretty much bought a PS3 for MGS4, Valkyria Chronicles, FFXIII: Versus (well, FFXIII was an excluse at the time too) and the new Kingdom Hearts, and I wouldn't complain about my purchase despite the high price 'cause I considered it worth it for what I've got/what I'm getting.
The PSP has plenty of good games and being able to portably emulate stuff is great (sure my DS can emulate stuff up to Genesis/SNES, but there's issues with both and a bunch of SNES games I'd really be interested in playing/replaying are nigh unplayable).
If you're on the edge about purchasing one, maybe this list will help, it certainly made me much more keen to buy it even though I was more than happy to do so just for Dissidia, KH and Agito; spoilered for huge.
And I'm sure it's missing quite a few other worthwhile games.