Season 1: Rich vs. Kelly. Not much of a contest here. I do give credit to Kelly for winning 4 or 5 challenges in a row, but her flip-flopping on the alliance did her in. Sorry, this is survivor not ethical dillema. I wouldn't run to the polls for either one of them due to their real life run-ins with the law.
My vote: Rich (reluctantly)

Season 2: Tina vs. Colby. Strategically speaking, i think Tina was better than Colby. She was instrumental in getting Ogakor off their losing track by switching to voting off Mitchell instead of Keith, which saved the tribe. But as I said, her performance in episode 2 was just terrible, she's lucky the tribe didn't follow her advice and vote her off. My vote: Colby

Season 3: Ethan vs. Kim J. For most of the game, both were just average players. Neither did anthing particularly horrible or great. But towards the end of the game, Kim proved something to me. When the cards were down at F4 (other 3 people in an alliance), she stayed with it and won the last 2 immunity challenges, including the last one which was a physcial challenge against 2 younger, more athletic males. that proved survival to me. Alot of people rag on Kim for not going with the female alliance of Kim and Theresa, but Kim J said it best in her post interview (everyone that switched alliances got gooned) and it's true. There were alot of dumb people on that jury (Frank congratulating on Ethan making that far but not Kim, Kelly being bitter and voting at random, Theresa having some unexplained fondess for Ethan, and Tom and Lex voting with the old boys club." ) My vote: Kim J.

Season 8: Rob vs. Amber. The voting was essentially meaningless since both were going to win in a manner of speaking regardless of the voting. But Rob deserves credit for running the table on 16 other supposed all stars. Anytime you can make experts look like newbies, it deserves a win. My vote: Rob.