There's just something about watching the original cast together that I really enjoy; even if it's in a bad movie like TFF. To me, the cast, and their chemistry, makes TFF watchable. I think it's better than any of the TNG movies and certainly better than STID.
While TFF wasn't good, I do think its short comings were exaggerated. It's the 6th or 7th best Star Trek movie ever made.