Ignoring the comment about FF being a bad series (certainly not the best series IMO, but not bad either), FF5 is one of my favourites. The characters and story aren't the best (except for Gilgamesh!), but I really liked the job system, the game kept me occupied for quite a while (the game was pretty long and had a good few sidequests), and Gilgamesh is the best enemy in any FF(!!).
I really liked FF7. It's not my favourite FF game, but it's pretty close. The story and characters are decent (not my favourite, but good enough to keep me interested), I like the materia system as it gives you a lot of options, I really like the music (especially Still More Fighting), the graphics are top-knotch (with the exception of the character models of course), and, like FF5, there is quite a bit to do sidequest-wise.