I think it question of what should be achieved by this commercial port.
Do you want to attract mainstream, hardcore or casual gamers? Each of these groups prefer something else.
I believe the goal of this port it to convice people to buy the Pandora. From this point of view the ported game should be known among wider audience so some older AAA commercial title would be better than any newer independent game. It should also show what's Pandora capable of (graphics, wifi).
My tips (in no order):
Dreamcast ports
Typing of the dead - ideal for Pandora's QWERTY
Space Channel 5 (part 2)
Jet Set Radio
Rez - well, it's on XBLA now, so probably impossible. Still wonderful game with nice grapics and sound.
Soul Calibur - same as Rez.
...
- there are so many great games on DC it's hard to choose one
PC:
Ultima Online - this one is older but could nicely show potential of wifi/3G multiplayer and QWERTY.
Doom 3/Half-life - I don't think anyone would play these on Pandora. It would be rather techdemo.
Re-Volt - someone mentioned already. The best RC racing game up to date. Still beautiful graphics.
Starcraft - some people are still mad about this one.
But to be honest, I don't think any of these games will make it to Pandora as it's question of money. Little consumer base means only few potentional costumers...