Let's talk about the usual suspects. The Yankees have a nice bullpen, and the Red Sox have three guys in there that can be closers for most teams. Now onto other teams. The Athletics looks pretty good too. The Dodgers have a solid pen. The Orioles don't look too bad either. Oh, and don't forget the Padres, Phillies and Rangers.
To save time, let's just compare 3 people in each bullpen.
Athletics: Bailey is a solid closer. Fuentes may be shaky in the past few years, but he's is still a good reliever. Balfour rounds out the trio, and he's a solid reliever too.
Dodgers: Broxton got banged around a bit the past summer, but he has a good track record, and he's still pretty young. Kuo and Guerrier will probably do well as setup-men, and they step in and close when Broxton falters.
Orioles: Gregg is certainly not fantastic, but he's consistently tolerable. Gonzalez and Uehara are fine pitchers who will help shorten the game.
Padres: Adams and Gregerson are fine setup men and they are a solid bridge to Bell, one of the best closers in the game today.
Phillies: Lidge is ok, and Contreras and Madson performs.
Rangers: I'll go with the depth chart for now. Feliz is absolutely reliable as the closer,and Rhodes and Oliver are fine lefties who continue to defy age.
Red Sox: Papelbon, Bard and Jenks. Three legit closers. Three reliable arms (at times).
Yankees: If Rivera wasn't enough, Soriano will close the gap. Robertson will help, and not hurt the team.
Cubs: Marmol and Wood are high K and high BB pitchers. Marshall the lefty is a nice complementary piece to the other two, with good strikeout rate but a lower BB rate.
I'd say that the Cubs aren't even in the top 3.
1) Red Sox
The Sox, of course, with their three closers, wins the top spot.
The Padres deserves the second spot, with three solid and reliable arms. However, they can't match the awesomeness of three closers.
The Yankees, with Robertson, a good but not great reliever, gets the third place. If they had a better player to join Rivera and Soriano, they'd have the best bullpen.