My favorites:
Calvin and Hobbes - The gold standard, IMHO.
Far Side
Foxtrot
Peanuts
Red Meat - Surreal, but sometimes achingly funny comic you see in a lot of alternative press publications. I hate you Milkman Dan!
My least favorites:
Dagwood
All of the Apartment 3G/Mary Worth type strips - I don’t like dramatic comic strips much.
This Modern World - vile ultra-lefty spew that you see in local alternative press publications, and on sites like DailyKos.
Bagpipe Cat - the cat who loves bagpipes, Ayn Rand, and Guinness Stout:
Not funny!
Bad enough that they're good: Red Meat, and Rehabilitating Mr. Wiggles (defunct)
Good: Bizarro, Get Fuzzy, Family Circus, Day by Day, For Better or Worse, and I liked Cathy. Why? The artwork was horrible, but it was a time capsule of the 70s-90s neurotic working woman.
Too corny for words: Ziggy