Howard vs. Jerry
When I first started watching this show again after several years I was struck by how annoying and demanding Howard and Jerry were. After watching it for a few weeks though, Howard has grown on me. His naiveté and complete dependence on the Hartleys makes him kind of sweet and likeable. He's like a big kid who would be lost without Bob and Emily.
Jerry, on the other hand, I find to be a completely unlikable character. He's rude, conceited, arrogant, and selfish. I can't see why Bob calls him his best friend, surely Bob can do better.