Man was Calvin & Hobbes awesome. IMNSHO every comic strip currently in print still lives in its shadow. C&H had it all - good illustration, good writing, life insight. It was a real life line for weird kids.
I don't know. The farside is pretty good, as well as Pearls Before Swine. Oh, and Cyanide and Happiness.
None of them reach the meta level of social/theological commentary that C&H did, but they're still really, really good on their own, doing their own things.