Thinking about it more, there are actually a lot of good boxing announcers. Honestly, I hate Leonard and tune him out whenever he talks, so I'll take people's word for it that he was subpar. But, Roy Jones does an excellent job. He's not super articulate, but if he tells you that a fighter is vulnerable to hooks to the body, chances are that fighter is going down from a body shot. He knows the sport so well and can really get into the technique without being pedantic. Andre Ward also does a great job, though his affect is a bit flat. He's another guy who knows the sport inside and out, and it doesn't hurt that he's still a top 3 pound for pound guy. Paulie Malinaggi is probably my favorite - very knowledgeable, knows most of the fighters personally and is fun to listen to. He stays positive but is not afraid to call guys out.
Mauro also does a great job - he's got a good voice and let's the action unfold. He also rises to the occasion and let's you feel the action. The HBO crew besides Jones/Ward is pretty meh. Lampley loves hearing himself talk too much and is too fond of leaning on his rote phrases - "battered from pillar to post" etc. He, like Kellerman, is also way too prone to pick a narrative and stick with it throughout the fight. Once you can tell which fighter they're pulling for it can be pretty absurd as they crow about jabs that barely land for their guy, then ignore hard hooks from the other fighter. So many times I'll watch a fight on HBO and feel like what I'm watching and what they're watching are two different fights. I used to like Kellerman when he was a wide-eyed boxing nerd, but now he's pretentious and another bandwagon announcer. Plus, for a guy whose only fight on record was with his girlfriend, he's very eager to call out professional fighters' hearts and chins. Actually, Lampley is another guy who likes to hit women. In sum, there are a lot of good announcers out there, but fuck HBO except for Jones and Ward.