Belichick was outstanding way before he was even at NE. He was a Defensive coordinator (2 superbowl wins with NY) for one of the best ranked NFL Defenses of all time. How is that not great?
He was great before huh? You need to check out his record before Tom Brady then. From 1991 to 2000 he had ONE winning season as a HC. Sorry that's not great. Being a good coordinator doesn't mean crap. RC, Charlie Weis, Josh McDaniel are all good coordinators but sucked or suck as HC. Sorry being good as a level 2 guy doesn't mean you're great.
The D's he coached in NY only had LT (one of the best players ever) on it and some other very solid players to work with. Keep trying though.