Some think the show lost something after the first two seasons. This might be due to the fact that it was no longer new and fresh, as well as the loss of Nancy Marchand, who of course played Livia - Tony's mother.

Personally, while even the most die hard Sopranos fan (including myself) can nitpick any number of problems from beginning to end, I think seasons 1-5 were solid.

But I can't say the same for Season 6, parts I and II. It should be remembered that Chase only planned on there being four seasons to begin with. Money talked and a 5th one was done. But after that I think the writers were running low on strong material. In hindsight, I don't think they had enough for 21 more episodes, which parts I and II consisted of. They basically just treaded water, without things generally being moved forward, until the end when things suddenly sped up with the NY/NJ war.

I would have much preferred that they do just a regular 13 episode 6th season. Everything was set up for that at the end of season 5 and there would have been just enough material and plot to wind things up strongly rather than drag things out just to make more money.

All that said, even on it's worst day The Sopranos was head and shoulders above 99% of anything else on TV. And over all is the single greatest TV drama of all time.