Over the course of my years and particularly through the use of MLB.tv, I have encountered and listened to many teams' announcers. What follows is my personal, 100% subjective ranking of them. There is no formula. Feel free to disagree with as many of these as you'd like. How you feel about broadcast crews is a matter of taste, and I don't expect that everyone's tastes align with my own. This is just something to start a dialogue.
If a team isn't listed, assume I haven't listened to them. As you can imagine, this goes for a lot of the NL.
Tier 1 (My favorites)
Mariners: I know I'm biased, but any broadcast that can balance the lovably enthusiastic Dave Sims, the lovably unaware Dave Niehaus, and conversations about UZR and The Hardball Times is a broadcast I can dig. I've heard lots of fans of other teams complain about our group, but as far as I'm concerned, realistically I couldn't ask for a better collection of guys to be the voice of my favorite team.
Red Sox: Having gone to a four-year college in New England, I watched a lot of NESN, and though I hated the Red Sox and everything they stood for, I always enjoyed listening to Jerry and Don. They're funny, they're entertaining, they know their stuff, they don't take themselves too seriously...they're not the most intellectual team around, but I wouldn't expect them to be. They're announcers, and they're excellent at what they do. By far my favorite part of the whole Red Sox experience.
Giants: I love Jon Miller. Love him.
Nationals: Okay so this is a weird choice, since I haven't really ever listened to the Nationals broadcast in my life (and who has?), but there's one particular call of theirs that I'll never forget. Allow me to set the stage. The Nationals are 2.5 out of the wild card in the middle of September, while the 72-74 are leading their division. Facing San Diego, it's 5-0 Washington in the bottom of the ninth.
Jay Bergmann pitching
Go here, scroll down to the 17th, and watch the clip of Greene's grand slam. I don't even know if that guy is still around in the same capacity, but as my first and only exposure to the Washington broadcast crew, I don't think I could've had a more fitting experience.
Slays me every time.
Tier 2 (Enjoyable but missing a certain something)
Yankees: Lots of people love to complain about Michael Kay's sensational voice and tendency towards histrionics, but I find him to be generally agreeable most of the time, and pleasantly objective. He's not my favorite announcer, and the guys with him are usually lousy, but I feel like this broadcast gets a bad rap. Go beyond the trademark home run call and it's a pretty good show.
Rays: I watched the Rays an awful lot a year ago, and though nothing stands out and I don't really have any anecdotes, I seem to recall them being all right and not the least bit objectionable. I just remember not liking one of the voices. I think it was Staats. Dewayne Staats? Really? I don't know what black people were thinking when they took that name from us. It's horrible.
Orioles: Jim Palmer never ceases to come off like a giant tool, but Gary Thorne possesses maybe my favorite all-time voice in broadcasting, and because of his work with the NHL when I was growing up he also has sentimental value. It doesn't hurt that, on top of that, he tends to know what he's talking about.
Dodgers: I'm sure a lot of people will raise all kinds of hell for my not making Scully a Tier 1, but he's just not my style. Is that so wrong? Yeah, I get it. You have wonderful memories of listening to Dodger games on the radio and having Scully paint a vivid picture of everything taking place on the field. But I just like my announcers to get a little excited is all. While Scully's great at what he does, there are other guys I like more. I can appreciate that Mozart was a phenomenal talent, but I'd rather listen to Grieg.
Diamondbacks: I don't know much about this one except that they use Win Expectancy sometimes and Mark Grace is a crazy person.
Padres: I'll be honest, I haven't watched a lot of Padres game this year, but they did find a guy who sounds just like Matt Vasgersian to replace Matt Vasgersian, and that scores major points because Vasgersian might've been my favorite announcer of all time. A year ago these guys would've been an easy Tier 1, if not Tier 0. Now they get a sort of speculative and residual Tier 2. Mark Grant is goofy in a way that doesn't drive me bananas.
Tier 3 (Ordinary, unremarkable, and/or boring)
Blue Jays: I know I've watched Blue Jay games before, but I don't remember the first thing about what their broadcast was like. However, I would remember stupid, so I'm putting them here because I've no reason to think they're bad.
Twins: Bert Blyleven makes it really really hard to want him in the Hall of Fame. But outside of his little quirks I find this broadcast to be pretty vanilla.
Indians, Royals, A's: I'm putting all three of them together because all three of them share a common propensity to lull me to sleep. I don't really take naps. I find that, whenever I wake up from a nap, I'm all out of sorts for a couple hours. But every time I'm watching one of these broadcasts I find myself leaning back and positioning myself in my chair in a way I consider least conducive to falling out and hurting myself should I drift off. I don't know how many times I've been watching a game against one of these teams and had the scoreboard suddenly skip ahead a few innings because the announcers' voices sapped me of the energy necessary to complete the second half of a blink.
The worst of the three is Cleveland because those guys had the audacity to call our defense bad the other week.
Tier 4 (Annoying and/or stupid)
Rangers: Annoying and stupid. Shut up, Jim Knox. Shut up shut up shut up shut up shut up
Tier 5 (Complete and total retards)
White Sox: Everybody hates these guys for a reason. I swear to God, more people know the White Sox for their broadcast than for their baseball. Hawk Harrelson is so bad that when I was watching a Red Sox game and they had him on as a guest, he dragged an entire inning down from Tier 1 to Tier 4. He's won five Emmys (ed. note: Emmies?)! Five! Jesus, I can't get my train of thought. Get? Find? These guys make me so angry I don't even remember which verb to use when describing your condition after losing your train of thought. I guess I don't really have to write much here since it's become almost trite to rip these guys to pieces. They suck. Ye gods do they ever suck. The good news is that Darrin Jackson moved to radio, but when you've got Hawk on the broadcast it's hard to notice anyone else.
Angels: Most of the time, Angel fans don't agree with me on anything, so I think it says something when even they can't stand their own announcers. Physioc has this air of pompous insincerity about him, like a more prevalent Rick Rizzs, but at least Rizzs has a good voice. He also has this way of speaking that makes him sound kind of leery and dubious, like no matter what he's talking about, he picks his words very carefully because he thinks that things could change any second. I dunno, it's a difficult quality to put into words, but it drives me crazy. He makes confident statements sound smug but uncertain. And then there's Hudler. For a guy who spent 21 years in professional baseball, Hudler doesn't seem to have a very good idea of how the game is won. But that doesn't stop him from making obnoxious interjections whenever he sees fit. Cliches! Cliches! Have you heard these cliches? The cutesy little nicknames ("The Wizard of O.C."?) just put him over the top. He's way too high-strung for a guy who smokes so much weed.