Looking around the league I would have to say that these teams have the best rotations...
Cubs
1. Zambrano
2. Harden
3. Dempster
4. Lilly
5. Marquis

DBacks
1. Webb
2. Haren
3. Davis
4. Scherzer
5. Petit

Phils
1. Hamels
2. Myers
3. Blanton
4. Moyer
5. Happ

Reds
1. Harang
2. Volquez
3. Arroyo
4. Cueto
5. Owings/Bailey

From my perspective I would have to say we are probably third right now, with the cubs as first and the phils are very close second. If either team gets lowe or if the cubs get peavy they would be pretty far ahead of everyone else.
However if Harang regains form, Volquez and arroyo pitch like last year and Cueto and Bailey take some steps forward we could potentially have the best rotation in baseball.
I didnt include the marlins but looking at their pitchers they might have the most talent there just really young and inexperienced.