I certainly don't blame Jim Davis for "selling out". He made a marketable character, and I don't blame him for trying to make his money because of it. I don't have a ton of artistic talent but if I created a lovable comic character and someone offered me a dumptruck full of money to sell toys and t-shirts and cartoons, I'm pretty sure I would take it, and I might even take it even if I felt like it diminished my vision of the comic. I would like to think I have integrity, and I think I do to some extent (there are certain types of companies I will not work for e.g. casinos), but Waterson is on another level.
And I have to say, it has made Calvin and Hobbes age a lot better for me. Garfield is almost more of a "brand" than a comic at this point, and it has made it such that I find the character and even the comics kind of (for want of a better word) "cheap" or "tacky". The same can be said for Dilbert (Scott Adams himself not withstanding...I used to genuinely like the comics).
C&H, on the other hand, reads about as well now as it did when I was a kid. The jokes still work, the art is appealing, and since there hasn't been this mass-marketing push for it, it has retained a purity unlike anything else.
I don't have the integrity or will power that Bill Waterson has, and I probably never will, but it can be something I strive to have some day.