Jerry Sloan is arguably the best coach ever. Most will go with Red, or Riley, or Pop or Phil Jax because they got the hardware, but I believe that anybody who knows the game well will recognize Sloan as one of the greatest and as a guy who is at least as good as the very best the NBA has see.
He coaches 22 years in Utah, and several times had seasons that were worthy of the COY award.
90: 55 wins (his first full season as Jazz head coach marked a 15-game improvement, the award went to Pat Riley who got 63 wins out of LAL)
95: 60 wins (Del Harris won, helping improve LAL from 33 to 48 wins)
97: 64 wins (Pat Riley won, helping Miami improve from 48 to 61 wins)
98: 62 wins (Larry Bird won helping Ind improve from 39 wins to 58)
99: league best 37 wins (went to Mike Dunleavy, who coached Portland the year before, but helped them improve their winning percentage)
04: Jazz lost 3 HOF players (Stockton, Malone and Mark Jackson), but Sloan still got them to 42-40 despite most expecting them to finish with less than 20 wins. (Hubie Brown won COY, helping them improve from 28 wins to 50)
06: 41 wins, an improvement from 26 wins (COY went to Avery Johnson who coached the Mavs to 60 wins but that was only a 2-game improvement form the prior season).
In most instances, the guys who won really deserved it, but seriously... at some point you just HAVE to give it to him, no?
On a side note: Once Pop retires, will a team ever have a career coach like Sloan or Pop? It seems teams are too eager to fire a guy, while great coaches (Doc) have no interest in coaching a lottery team.