I'm a huge Kevin Smith fan. Clerks is on my all-time favorite list. I'll be freaking camping out the night before Clerks II opens.
My opinion of his main movies...
Dumb movies that just went for the laughs:
Clerks: Possibly the best indie flick ever made
Mallrats: Generally considered his worst. He's basically disowned it. He didn't really know what to do with a large budget. Good for a few dumb laughs, and that's about it.
Jay & Silent Bob Strike Back: Excellent. Brings together all the characters he's created.
Movies where he made an attempt to make an actual film:
Chasing Amy: Awesome. Probably his best "real" movie. Good mix of drama and comedy.
Jersey Girl: Never saw it. Smith made it because he was a new father and it seemed like the right type of movie to do. Which means I had no desire to bother with it.
Dogma: Pretty good, but a little overrated. Gets a little carried away with its self-importance, but mostly works. Clever in many ways.