Pokemon Red is 0 minutes long. That might be a good run for you.
Seriously, though. You may wish to take a look through this list. It's sorted by run time, and you should be able to find some good RPGs there. Of course, runs are always changing, so times may be faster than what is listed.
EDIT: doicm beat me. Still, take a look through the list.
Well just looking through the list for Final Fantasy games, FFL2 is under 40 minutes, FFL1 is under 70 minutes, FFIII NES (specifically, dunno about DS/PSP one) is under 90 minutes and FF1 PSP (specifically, because of the equip trick) is also under 90 minutes.