Phantasy Star 2, without a doubt a game ahead of its time when it was released on the Genesis years ago.  While it may look simplistic now compared to the recent RPG's of late, but everything from the anime style graphics to the excessively long quest made Phantasy Star 2 worth playing.  The final boss was one of the most memorable bosses in video game history, when I was younger it gave me nightmares.  All in all, if you can find it now it may be a bit pricey, but next to Gunstar Heroes, this is the second best Genesis game ever.