Nah, most definitely not. Most people say it's the weakest, because the whole serial killer plot is rather unrealistic and some characters behave strangely. Personally, I still like it, though. But not the best by a long shot. (For me, it's 2. Bit of an uncommon opinion, though.)

Season 5 is usually considered the worst, although at first some people dislike season 2, because of change of focus from the hood to the docks.

However, once you see the entire show, Season 2 is perfectly placed and and works amazing with the rest of the show.