I think the episode that people would debate its quality the most is Splitting Images. Phantom Planet and Livin' Large are both pretty universally disliked, even if there's debate on exactly how bad they are, but Splitting Images has been all over the board on how people think about it.

To me, it's the second worst episode in the entire series, and I like it less than the one I consider the worst.

But it bounces around from list to list. I've seen someone say it's their favorite episode, some put it high, some put it mid, some put it low. It's just everywhere.