I absolutely ADORREEEE Final Fantasy III, for the SNES.
I'm not exactly a fan of the series, but that is actually the first FF game I ever played, and it's still my favorite of the series, and of all games.
I use to sit up when I was twelve at my friends house with his copy of it that was chewed up by his dog and beat it in a sitting, those were the days, when I had time to do those kinds of things. Even if they weren't the healthiest. xP
I also like Shining Force I and II for the Genesis.
And have yet to play the SegaCD ones, but I can't wait. ^^
And GainGround for Genesis if you just want an easy to play two player game.
I find it more of a thing to sit around and talk while playing than to actually get into, it's not too difficult, but I think it's fun. ^^