Your list of favorites shows how subjective it is to choose the "best" of any food product. I have never tried Tim Horton's, but there is no way I would rate Caribou, McDonald's and Seattle's Best ahead of Starbucks. Of the ones I have tried, I'd have to go:

Peet's
Starbucks
Dunn Bros.
Seattle's Best
Tully's
McD's
Caribou

By the way, if you want coffee (including espresso) that blows away even Peet's, try Intelligentsia in Chicago. There are only a handful of stores (and I believe now one in LA), so I didn't include it on the list of chains above. Seems like it would've been kind of unfair....