The media would have you believe that the Red Sox or Yankees have the best rotation in baseball. However, statistics prove otherwise. Neither the Yankees or Red Sox finished in the top 10 in starter ERA. The Yankees did add Javier Vazquez who lit it up in the National League for the Atlanta Braves, but that success likely won't translate to the American League, as in his previous stints with the White Sox his ERA was under 4.00 only once and never under 3.70.
AJ Burnett, the Yankees number two starter, also has never had an ERA under 3.00 in the American League. Andy Pettitte, who will likely be the Yankees number four starter, hasn't had an ERA under 4.00 since he was in Houston. Joba Chamberlain is showing that he should not be in the starting rotation as he really struggled to find his rhythm as a starter with an ERA near 5.00 while struggling down the stretch. The Yankees clearly believed this as well, as they cut his innings down considerably. It is possible that he could turn it around this year, but I honestly think that making him a starter was a mistake and he belongs in the bullpen, where he has proven to be dominant.
All of this leaves C.C. Sabathia, the staff ace, as the Yankees only "dominant pitcher". Now, this is not to say that the Yankees cannot be successful, as they do have a "good" pitching staff to compliment their great lineup, which did lead them to a World Series title last year.
The Red Sox also have been considered one of the best rotations. They added John Lackey to their impressive 1-2 punch of Jon Lester and Josh Beckett.
The problem for the Sox is they don't have much beyond their third starter. The Red Sox starters' ERA was 19th in the majors last season, and I don't think Lackey will be enough of an improvement to their rotation to make it elite. Many people will bring up the Atlanta Braves as one of the best rotations, but keep in mind they will be losing their ace in Javier Vazquez to the Yankees and he performed very well in the National League last season.
The Mariners, with the addition of Cliff Lee, and the Phillies, with the addition of Roy Halladay, certainly have the star-power to be considered one of the best rotations, but their depth is definitely lacking.
So, with all that in mind, here's a team to think about: the Chicago White Sox. At the top of the rotation, the White Sox feature a 1-2 punch of Jake Peavy and Mark Buerhle. Peavy has won a Cy Young in his career and is entering this season with a 17-inning scoreless streak for the White Sox after coming off an ankle injury. Buerhle is coming off another solid year going 13-10 with his signature 3.84 ERA, which is slightly over his career average, but still solid nonetheless.
John Danks, who is just 24 years old, posted another solid year and is likely to have another good year as this will be the fourth year as a starting pitcher. He is already posting solid numbers and is likely to improve upon those numbers while learning under Peavy and Buerhle. Gavin Floyd will be the fourth starter in this rotation and had a similar year to A.J. Burnett with 11 wins and a 4.06 ERA while posting 164 strikeouts. He also will most likely improve upon that with time learning how to pitch from Mark Buerhle.
This is a rotation of four very reliable starters, but they also have Freddy Garcia in this rotation, who when healthy has proved to be a very good starting pitcher. Questions still remain about whether he can stay healthy because he hasn't been given an opportunity for a full year of starting. This year he will be given a chance and possibly bolster the very impressive rotation of the Chicago White Sox.
Another team that has a very good rotation that can compete with the Chicago White Sox is the San Francisco Giants. They have a plethora of good starting pitching. The Giants have the two-time consecutive Cy Young award winner, Tim Lincecum, at the top of their rotation, coming off a 15-7 2.48 ERA with 261 strikeouts followed by Matt Cain (coming off a very solid season at 14-8 with a 2.89 ERA) and Barry Zito (who after a slow start had a very strong month of August and a good final start, as he finished the season 10-13 with a 4.03 ERA and showed much more improvement with his command).
They also have Johnathan Sanchez who had a decent season finishing with a 4.24 ERA, but really heated up at the end of the year as after July 1st he lowered his ERA from 5.45 to 4.24 and also thew a no-hitter.
The only problem with the Giants rotation is that they don't currently have a proven fifth starter, but they have four solid starters. The Giants just do not have quite the depth that the White Sox enjoy, who have a fifth starter in Freddy Garcia to plug in, but their rotation is still very impressive.
You could make an argument for a few other teams, but I don't think any rotations are as deep as the Giants or White Sox. We'll see whose rotation is best when April rolls around, but until then, let the debate begin.