Gus Johnson is so over the top. I hate his voice in Madden and I'm glad I don't have to hear it on live broadcasts.
I LOVE LOVE LOVE Al Michaels. His voice is amazing. I don't know what it is, but it just has this presence about it. I don't even care what he actually says.
I don't mind Cris Collinsworth. He occasionally has interesting thing to say, but he often reiterates himself. Many times he echoes the prerecorded lines he uses in the Madden series, which I know by heart by now.
Jim Nantz and Phil Simms are neither good nor bad. I barely notice them. I don't really hate any announcer and I don't find any real anti-Patriot bias in any announcer, just lack of knowledge. Simms/Nantz seem to know the most about the Patriots while Cris Collinsworth seems to know all the interesting bits of history.
Overall though, I prefer SNF on NBC. I like how they present the players in street clothes in the little cut scenes, the production, it's all very nice, sharp and presentable, almost like a play with characters. CBS's production could use some polish.
Fox's is okay. Was better when they put more effort into production, which they seem to improve for the playoffs.
I really enjoy the special Cleatus spots they make. (The Fox NFL robot). It was amusing when the Terminator TV series was airing - it fought a Terminator.
The Terminator vs FOX Robot - YouTube
Also, you just can't beat the FOX on NFL theme song. No other song embodies the NFL better. Here it is with Cleatus doing what looks like a kickoff return against other robots:
NFL on Fox Transformer Edition - YouTube