My faves are the EuroSport team of Dave Harmon and Sean Kelly. Their commentary is well-informed, Sean knows a ton (and if you're not challenged by accents, he's whip-smart and well-spoken), and they know the field far better than Liggett and Sherwin.
As was mentioned before, Liggett's prime days were during the heyday of Hinault, LeMond, Fignon and Indurain. Since then, he's lost some focus, likely due to his wearing too many hats during these races. I often get the feeling that Liggett is "phoning in" his commentary, using the same tired clichés that, while he coined the phrases for most, are simply worn out.
And I think that Schlanger and Gogulski are coming along just fine. These days, in fact, I prefer them to Liggett and Sherwin. And I love hearing Magnus Backstedt on Cycling.tv, as his perspective is current.