Seasons 1, 2, and 3 are just utter, utter perfection. I have a soft spot for a lot of Season 4 episodes, too. Best episode ever, though? The One Where No One's Ready. It's 22 real-time minutes of what the show does best--the six of them in a room together. It's so. awesome. In these early seasons, when the characters hadn't yet become caricatures of themselves, there was a LOT of really great dramatic/emotional moments, too. I don't think the cast gets enough credit for the more serious sides of the characters they portrayed. Again, in the early days.