Most fans agree that Season 1 is the best -- quite a few would say it's the only good one, in fact. I wouldn't quite
go that far, but subsequent seasons were definitely of lower quality than the first.
So, yeah, Season 1 had some good stuff. Season 2 was a mixed bag, with a number of dumb episodes, but it picked up a bit towards the end. Seasons 3 and 4 were halfway decent. Season 5 was almost like a completely different show, which in and of itself might not have been so bad, but unfortunately the execution was terrible; as a result, the final season was mostly a mess.