[decha]

I found a great comparison table.
There are just few candidates. We should fill this out.
Major League Pitchers and their 'Net' Performance - Communipare

[teamera2008]

Not a very good comparison when you leave off Brandon Webb

Webb's career ERA of 3.19 is better then Santana's(3.22), Halladay's(3.62), Peavey's(3.27), Beckett's(3.76) and Wang's(3.75)
Active Leaders & Records for ERA - Baseball-Reference.com

and Webb's Adjusted ERA+ of 145 is better then all the players listed
Active Leaders & Records for Adjusted ERA+ - Baseball-Reference.com