I generally judge a crew not by their insight but by the way the add atmosphere to the game. This is why I have nothing against Joe Buck. He may be wooden and soulless, and struggles to conceal how much he hates his life, but he brings an element to big games the way no other announcer does.
John Madden was dumb, but he was fun. Dan Dierdorf was really dumb, but added good atmosphere to games. And so on. Maybe it's because I watched WWF at it's peak in the late 90's, but I'm a believer that announcing plays a pivotal role in the presentation of 'sports entertainment.' Dumb or not, it can still make it more fun to watch.
Occasionally though, you'll see a color commentator with a gift for insight. Mayock and Huard are pretty good, though my favorite is 80's beard. He just gets Pete Carroll in a way that no one else on TV does. Shame he had to move on because of his tendency for petty flubs. Expecting people to talk and react in real time for 3 hours without ever making a mistake is silly and unrealistic. I never understood why so many people freak out over that kind of thing, but maybe that's because I've interned at a Network TV station and they haven't.
Can't imagine watching the game on mute. Even the worst announcer crew in the world wouldn't be enough for me to sacrifice the sounds of the game.
Right now my favorite NFL crew is probably Albert/Moose/Goose. Each has their flaws but combined they add a lot of atmosphere to games. I also like the Aikman/Buck crew for big games. Al Michaels adds a ton of atmosphere to his games. Favorite football announcer is Gus Johnson. Favorite football commentator is Tim Ryan followed by Mike Mayock followed by Charles Davis and Brock Huard.
For baseball, Dave Sims is underrated and Mike Blowers is insanely underrated. Blowers is an insight machine and is about as close as humanly possible to being mistake free. He's humble in demeanor as well. The perfect color commentator.
For Radio, Rable is awesome in a 'northwest weird' way, he fits the hawks like a glove. I always enjoyed Dave Logan for the Bronco's games, even though he's super generic and a total homer. But he's polished with great voice talent. He's another guy that perfectly suits his region and fanbase. I used to listen to Rockies games on the radio ten years ago and the announcer was really great, shame I can't remember his name.
If there was a thread like this for the talking heads of the industry, I really like the way Bomani Jones looks at the world. His commentary on Wilson "not being black enough" was honest and spot on.