My favorite webcomic is probably
Aetheria Epics. Probably because of a combination of the art, and the interactivity.
...or
axecop for the sheer ridiculousness.
I can't really say I like webcomics about gamers, because the couple I've read are basically just commentary on games and don't really have enough substance on their own.
Comics with games as part of the core mechanics are way different story though. I enjoy OOTS, ERF, and Keychain of Creation.
I comics are only webcomics, if they're web exclusive, or at least appeared on the web first. Not that the title is terribly important.