"The best you have ever seen?"
With all due respect, he is #2 or 3. Yes, Stevens did an amazing job getting Butler to back-to-back National Title games (particularly with that 2010-2011 team that lost to us). He has also proven to be a top notch NBA coach, as well.
But there is no one during the modern era who has been better than Jim Calhoun. No One.
Calhoun built University of Connecticut men's basketball to a level that no one other than himself could ever imagine. People forget that things were so bad around here that we had a task force formed by then President John Casteen to look seriously into the pros and cons of withdrawing from the Big East not long before he was hired because our school leadership at the time was unsure if we would ever be able to compete.
Not to diminish Stevens - he has been and continues to be great. But the best ever? That title can only go to one person, and in this case it is Calhoun who rightfully earned that title. And when Stevens' Butler team had the chance to beat Coach K and Duke in the 2010 Title game - they came up just short. When Calhoun had the same chance against an arguably even better Duke team in 1999? He won. 1 of 3 National Titles. Not even mentioning the 2011 Title game where Calhoun won head-to-head because I agree it was an amazing job by Stevens to even get that particular Butler team to that game. But with all else being equal, the difference in results versus Duke in the title game, combined with 3 Titles won vs. 0 has to give Calhoun the nod.
I think there is a difference between greatest basketball coach and best basketball coach.
Calhoun is an all-time great, top 5 coaches all time since he built a nothing program into a national power and 4 time championship program.
I am all for counting championships as a primary factor, but sometimes I think it's splitting hairs when you count championships. If you look at it, Stevens was literally inches away from 1 title and a game away from another. Belichick and Brady could easily be 3-6 or 7-2 in Super Bowls. Yes, what's done is done and you can't say "what if" or change the past. But the fact of the matter is I've never seen a coach maximize such little talent at both the college and professional level like Brad Stevens has. The 2010,2011 Butler team and the Celtics teams of his first few years reached levels they had no business being at.
Calhoun is one of the best program builders of all time, maybe the best. Brad Stevens is the best I've ever seen at maximizing talent, analytics, in game Xs and Os, etc. It's hard to compare the two, but they are at the top of the game in their own respects.