Hockey Night in Canada. Not exactly a TV "Show", eh? Alright, best TV show's gotta be Scrubs, even though I haven't seen it on lately (used to be on Tuesdays, but not anymore, apparently). It's an awesome, hilarious show. The Simpsons, and Friends are awesome, too. My Wife and Kids and George Lopez are cool, but I only watch them when I'm really bored (and I think George Lopez got cancelled). Man, I'd love to say House, but I always miss the episodes, and I've never actually seen a full one, so I can't really get into it now. Same goes for Lost.
And worst TV show is Treasure Hunters, man. That's got the worst acting ever, and it's way too cheesy. Plus, the advertising is obvious (eg. "I got a Motorola Message!". Lame music in background as the "Motorola Message" plays with the announcer over-pronouncing every single word).