I dunno, hardware wise I think its pretty clear that PSP2>3DS>Ipod
So, as far as multiplatform games go I think the PSP2 would be the default choice.
All of these platforms offer cheap small downloadable titles (via eshop, psp mini/ps suite, app store) though larger budget titles seem to be mostly limited to the 3DS and PSP2 due to price points and control options.
However after that fact, what is really important is exclusive quality game content. Both 3DS and PSP2 will have this as a strong point.
This is an area where iOS games struggles as they are often very cheap disposable game experiences; and, if popular have a slew of shameless imitators. This leaves the consumer with an impossible chore of sifting though thousands upon thousands worthless of games, unless the consumer is told by marketing or by a mass consumer base which game to buy (and being told what to buy is never ideal as marketing would control success rather than game quality).
