Season 1 was BRILLIANT. I think halfway through season 3, it got A LOT better.
Tracy's parking scene where she turned everyone into ice was EPIC. Also the fight between Sylar, Pete and Nathan was awesome.
But then it went downhill once again on Season 4.
Season 3 was better than people make it out to be and Season 2 would have been completely different if it wasn't for the WGA strike in 2007. The point where Heroes really hit the stride was with S4.
I hope Tim Kring has nothing to do with this. He ruined all of the characters, especially Claire; Claire went from being my favorite character to the most annoying one.
He wasted Hayden's and Ali's potential with horrible story plots.