There are 3 layers that serve as a huge help for BB the general manager (and at least one - average original draft position - that serves as a major impediment), which is part of what makes it so difficult to nail down exactly where BB belongs among GMs:
1.) Has Brady as his QB
2.) Has Bill Belichick as his H.C.
3.) Has a team playing in the AFCE, which has largely been down for over a decade
Comparing BB the GM to someone like, for example, Kevin Colbert, becomes almost an impossible task as a result. Is BB a good GM overall? That seems like the answer would be an undeniable "yes". Is he the best, or among the top 2-3, or the most successful, nevermind "by far the most successful"? That's much more questionable, and gets into a lot of different variables.