Totally on board with Bill Walsh. I'd probably consider Shula as well. He only won 2 Super Bowls, but he is the only coach to get the perfect season. Belichick had the chance, but in my opinion, got out coached by Tom Coughlin.
Don Shula was also great at coaching to the strength of his players. When he had a good running game, he ran. When he got Marino, he threw. When Jimmy Johnson took over the Dolphins, he tried to force his run-focus game into a team with a HOF QB.