Just gonna spitball here...
I don't think I am qualified per se, but I think Jim Harbaugh and Pete Carroll are #1 and #2. The speed at which they turned those teams around is amazing, and there is a lot more to coaching than whether or not you decide to go for it on 4th and 6th.
I would say that the most important aspect of coaching is simply how well your team plays, and most of that is on talent evaluation and talent development. Pete's in game management is average at best, but he's unmatched as an evaluator and talent developer. He's also a very bright X's and O's guy for the most part (despite some of my nitpicks, I think he's brilliant) and he's done an incredible job evaluating and building his assistant coaching staff.
I don't think Jim Harbaugh is on that same level, but unlike Pete I wouldn't say he has any glaring deficiencies, and the way that he's gotten that defense and offense to over-achieve in a sustainable manner is incredible. I like CK, but I am pretty sure that almost anywhere else he'd be having a career along the lines of Dennis Dixon, Troy Smith, et al. I don't think I can overstate how impressive it is that Harbaugh managed the results he got out of two purely mechanical QBs.
John Harbaugh is a good coach, but I think he has a lot less to do with Baltimore's success than his brilliant GM. Ditto Mike McCarthy.
I like Tom Coughlin but he's not some brilliant mind or anything, just a tough guy that gets results, like a better, smarter, more effective version of Jim Mora.
Jeff Fisher should be up there, though I think he's a tad over-rated around here. He's pretty much the opposite of Carroll: sharp as a tack with in-game decisions but average at best when it comes to identifying and fostering young talent.
Bill Belichick sounds like a brilliant guy when he talks, and I actually like the cheater side of him. Wrong as it may have been, I see it as him just "thinking outside the box" to help his team win. "Cheating" is all but accepted in baseball (not HGH, but hiding pine tar on a baseball, stealing signals, etc), some would even argue it's an accepted art form. Some have argued that Belichick is just riding Brady's coattails, but Belicheck didn't inherit Brady. He drafted him, and oversaw his development. He also won 11 games with Matt Cassel in 2008.
Sean Payton always struck me as a cutting edge type coach. I don't know how much of the Saints mini-collapse last year had to do with his absence, but I do know that Drew Brees went from a frustrating talent to a Hall of Famer when he joined forces with Payton.
Last mention: Marvin Lewis. I don't know how many times he's been an inch away from getting a pink slip, but I've always respected the way he conducts business. I would argue that the Bengals have done the second best job acquiring and developing young talent over the last 3 years, after Seattle of course. Any coach that gets the kind of productivity after the 1st round that he's gotten in recent years should be paid close attention to.
