Hmm. In the order that I'll probably try them out...
1) Xenogears
It has brilliant mecha combat, a fantastic story, and for the age it looks very very pretty. I've been avoiding re-playing it for four years now, purely so that the next time I do will be on a handheld.
2) Chrono Cross
Didn't like it too much last time through, but I think it'll do better when I'm not trying to compare it to Chrono Trigger so much (because really, Cross and Trigger are actually fairly tangentially related, imo). I also happen to know that it's one of those problem games with crashes near the start on many psx emus, so it'll be something of a stress test for the Pandora one...
3) Intelligent Qube
Brilliant game, not especially taxing, but good for pick up and play factor.
4) Breath of Fire III/IV
Both are absolutely awesome, and among the best games I've played on the psx.
5) FF Origins.
Again, been avoiding playing it because I want to try it on a screen that'll do it justice.
6) Wip3out
Because by now I'll want to try a racing game and see how natural it feels.
7) Worms Armageddon
Because I'm shite at racing games with weapons, and after Wip3out, I'll probably want to blow some stuff up.
8) Moto Racer 2
Fun racing game on motorbikes that my PC always used to crash trying to run. Maybe the Psx version on Pandora will be friendlier?
9) Others that I haven't planned far enough ahead to slot in.
This includes the FF series (7-9 in particular), Klonoa (which I hear good things about), Resident Evil, Alone in the Dark, the Tales series, a whole host of other amazing RPGs that turned up on the psx, the psx incarnation of MegaMan, Ridge race, Spyro, and anything anyone has mentioned as being awesome that I can find in the bargain bin of the local gamestation.
I've been waiting for handheld psx emulation on a non-Sony console for a while now...