Honestly, I couldn't get behind patapon. Overall, the console is fine. The only thing that ever bugged me about it was the ghosting on the 1000 model, which I didn't own. Also annoying were the lack of dual stuck, or thumb knobs, or whatever. I didn't play any game on PSP that required free-control camera, though.
Mega Man Powered Up was my favorite game on the console, and the online servers are still up too, so you can download and share custom stages. Also good were Mega Man: Maverick Hunter X, and Tekken: Dark Resurrection. It's not called "Tekken 5: Dark Resurrection" because it's missing the vanilla Tekken 5 stages, which were nothing but recolors anyway. Gameplay is a 1-1 conversion from Tekken 5: Dark Resurrection, with the only other thing taking a hit being the graphics. The only 2 reasons I don't play it these days is simply because I have the game on PS3 and Tekken 7 usually gets my time when I want to play Tekken these days.
I'd opt for a large memory card around 32 GB, though. IIRC, if the card is too big, it'll have negative effects on read/write speeds. Should be enough for the PS1 games you'll also have access to.