The DS, by a long shot. And it gets even more outstretched if you get a DSLite and look at the GBA RPGs. Second place goes to the PSP, as there are quite a few gems on that one, more than are native to the PS3. (And the ability to access the PS1 classics is a nice bonus.) On the console side... I guess the 360 has a slight edge? But with future potential, I'd say all 3 are really about even. The PS2 easily beats them all.
-dunno001
-On a quest for the truly perfect game; I don't think it exists...