Since baseball is a regional sport, most people tend to root for the team that is geographically the closest to them. But there are a couple teams like the Cubs, Braves, Yankees, Dodgers, Red Sox, etc. that have huge national followings either because of years of success or national exposure.

In my experience though, teams like the Giants, Mets, Padres, White Sox, Blue Jays and Mariners all have among the best local broadcast crews. If you really wanna learn about the game from an intelligent former player, the best 4 color guys IMO are Steve Stone (White Sox), Mike Krukow (Giants), Ron Darling (Mets) and Mike Blowers (Mariners).

Sorry if my response was too long lol, but I hope that helps I guess.