I have just finished watching season 4 and I think it's the best season yet!
Ranking the four:
#1: Season 4
I think this is the most intimate season yet with rich character development and it was a perfect development from season 3.
#2: Season 1
I finished the whole season in 1 sitting. It was absorbing and the reason why this cable show has found its way to millions of viewers.
#3: Season 3
Mad Men almost lost me halfway through the second season and I have delayed on watching this season but from the 5th or 6th episode, it just got better and better.
#2: Season 2
This season was just a blur. I hardly remember anything that happened this season.