Best season -
Prison Break, Season 1.
CLEAR winner. Fast moving, edge of your seat, greatly written.
Best series overall -
Sopranos.
The writing really wasn't that good. But the actors in the mob were amazing.
Worst series overall -
Lost.
Was ok for a couple episodes. But the sci-fi aspect did not fit & made it horrible. To note though, I only watched through early 2nd season. But don't tell me the series somehow transformed.