It's hard for me to decide, but I'm still going with season 1, I think.
Perhaps it's just that there were too many things this season (4) that I know for a fact just couldn't happen that way in reality. :lol: It's good, of course, but it sort of took the tension out of the story for me to play along with it so much.
Even season 3, with its occasional frustrations, provided plenty of thrills and great drama. (Go, Michelle!)