Yes, a contributor to Cleveland Plain Dealer has actually done this. See if you agree with the rankings.
For me, the series was absolutely brilliant during its first two seasons. After that, things started to go in the direction of outlandish fantasy. And at that point, I could no longer suspend my disbelief.
They started to lose me when they introduced the woman with the samurai sword. Then there was the introduction of the small-time dictator (a staple plot device in post-apocalyptic fiction). The magic was gone.
But like I said, the first two seasons of The Walking Dead were absolutely brilliant, and far better than anything George Romero has ever done in the zombie genre.