Tales (Only played Phantasia and Symphonia, I really need to import the others)
Wild ARMs (Only played 1 and 3, stupidly)
Star Ocean (Really, only Star Ocean 1 & 2, TTEOT was awful)
Chrono Trigger & Cross (They're both long enough to count as a series)
Breath of Fire (Though missing out 3 and 4, I didn't get a chance to play them very much, so I can't really cover them much)

I don't really play so many RPGs any more, and the few sereii I consider really worthwhile are the ones that I either haven't played too much, or haven't excessively over-extended themselves, covering a few too many games of depreciating quality.