Season 2 is tough to swallow because it changes so much from season 1. I think people dislike 5 for the same reason. 2 and 5 are probably my favorites, however. They're the ones that most capably hit the overarching philosophical theme of the entire series the best.

One of the strengths of the show is changing it up (notice how they foreshadowed that theme for the show by saying that phrase several times in season 1), but at first this strikes people as a weakness, myself included