I ran across a blog dedicated to mocking webcomics the author feels are inferior. I initially stumbled across them because of their criticism of VG Cats, a comic one of my coworkers is inexplicably nuts over. I noticed they had a critique of Sluggy Freelance that was also dead on: the strip is long in the tooth because the artist can't conclude a storyline to save his life.
That said, the critic doesn't seem to realize that making a strip is hard. Creating deep characterization in a handful of panels is difficult. Dilbert has pretty poor art and shallow characterization, but is wildly successful. TV is the same way. For every sitcom with some depth like The Office, there are a dozen successful series with characters little better than "fat girl," "lazy kid," or "trouble-maker."