Grin & Bear It and Bloom County are (or were) the best topical cartoons.
Jeff MacNelly and Michael Ramirez the best editorial cartoons.
Calvin & Hobbes besides being very funny is also able to slip in philosophical questions. Arlo & Janis, The Grizzwells and The Born Loser are also all funny cartoons.
I should have added BC, Wizard of Id and Herman.