And no, as long as someone likes something that is considered art, there's no such thing as bad art.
Well liking something =/= it having good quality.
There is bad art. Cheap, uncreative and amateuristic. I see it everyday.
I loved the prequels, I basically know episode III by heart, but I do agree, that it's not that good movie-wise. It's not HORRIBLE as OP said, but it's not great. Still, I remeber the the CHAOS in theaters when it was released =)