Psone would be better. I think everyone here is looking at the n64 with rose coloured glasses. It only had a handful of good games. I can think of many PS1 games I would love to play on the handheld.
- Resident evil series
- Ridge racer series
- Silent Hill
- Marvel Vs. Capcom
- Crash Team Racing
- Tenchu
- GTA 1&2
- Final Fantasy I-IX! (I through V have remakes for PS1)
- Thrill Kill
- Megaman Legends 1&2 (Unless they are coming to North america someday on PSP)
- Grandia
And that's just some of my favourites.