Dusty Baker is terrible, plain and simple.
You could make a case for Ron Gardenhire. How he manages to make the Twins competitive every year is beyond me.
La Rusa is an egomaniac, but he's also one of the greats.
Mike Scioscia is a very good manager, but better than Francona? Tossup.
Joe Maddon is good, but he still has to prove he isn't a one-year wonder.
Bobby Cox is a great manager, but he has only one ring to show for all the consecutive seasons his Braves made the playoffs.
Joe Torre is a living legend.
Lou Piniella is good, but other than the Reds, he hasn't been able to get anything out of his ballclubs in October. The Cubs are 0-6 with him so far. And they weren't in any of the games. That Mariners team that won 116 games in 2001 didn't even get to the World Series.
Charlie Manuel hasn't done anything yet. Shouldn't have even been mentioned.
Leyland is good, but he's managed a lot of bad teams.