There's a spectrum running from Bill Watterson to Jim Davis, and I'm entitled to my opinion about where Randall Munroe falls on it. :P

Oh come on, Jim Davis at the bottom? Garfield may be terrible, but have you ever read Marmaduke?

Garfield is terrible; Garfield died some time around 1990. I don't remember the year exactly, but I distinctly remember the strip; it was a Garfield-stuffs-Odie's-mouth-with-a-watermelon-rind joke---exactly the same joke that had run a decade or so earlier.

But Garfield wasn't terrible. Go back and read the first five or six years of Garfield; at the time, it was a breath of fresh air.

For those who haven't seen them:

http://garfieldminusgarfield.net/

http://marmadukeexplained.blogspot.com/

Great arguments for transformative fair use if you ever need them.

You fail to account for ironic value.