Forbes has ranked all the general managers with at least 3 years experience from the 4 major sports (MLB, NFL, NHL, NBA). Detroit Tigers GM Dave Dombrowski came just about in the middle at 48th. In terms of baseball GMs though he did pretty well.
The highest rated baseball GM was Billy Beane at 26. Dombrowski ranked 9th among MLB general managers behind Beane, Minaya, Epstein, Sabean(?), Gillick, Schuerholz, Beinfest, and Jocketty.
If you’re wondering about the other Detroit general managers, only Joe Dumars garnered a favorable rank (9th). Red Wings GM Ken Holland came in 90th. Amazingly Matt Millen didn’t come in last (which is just one more reason to question the validity of the rankings), placing 96th out of 98 general managers.