Here's what I think.
Total Drama Island Winner: GwenGwen had more of a plot in TDI than Owen, and while I do love the big guy to death, Gwen deserved it more, after having to battle through her feelings for Trent and rivalry with Heather.
Total Drama Action Winner: DuncanThis one is less about Duncan deserving it more and about Beth deserving it less. Beth essentially just derped her way to the finale even more than Owen did, without really getting involved in anything besides Justin's plot.
Total Drama World Tour Winner: HeatherYeah, no real surprise here. While Alejandro is my personal favorite villain, his ending is unbelieveably stupid.
Total Drama Revenge of the Island Winner: CameronAgain, no real surprise. I don't exactly mind Lightning's ending, it's just that Cameron's feels so much more satisfying.
Total Drama All-Stars Winner: ZoeyLet's just say Zoey didn't wander around her head all season and hit an offensive button.
Total Drama Pahkitew Island Winner: ShawnI JUST WANT SHAWN AND JASMINE TO BE HAPPY OKAY???
- ahem* Sorry about that. Anyway, Shawn and Sky both worked hard for their win, and while I don't think either of them deserve it less, I just think Shawn's ending is a small bit more satisfying.