To me, I thought the show got better as the actors fully developed their characters over the years (notice the accent differences between season 1 and 5). It added a realistic feel to the show. But, come on, its The Sopranos! All the seasons were great!

My favs are: Season 5, 4, 6 Part II, 3, 2, 1 (mainly because I don't watch it as much as the later seasons), and then 6 part 1.