I'd like to state beforehand that I think Red Auerbach is the best coach of all and will always be the best coach of all time. The guy changed the game and built his dynasty from scratch.
That being said, in this era, a lot of people have Phil Jackson as the best coach. And he is a great coach, he gets the most out of his players, and he has won 11 titles, he gets championship caliber rosters to play like champions. However, he cherry picks his titles. Jordons gone, Phils gone, Shaq and Kobe are splitting up?? Phils gone. Dwight Howard going to LA?? Hey, Phil said he'll come back.
Gregg Poppovich doesnt have 11 titles. He has 4, if there is a god, soon to be 5. He'll never catch Jackson considering his age. But this guy has had the Spurs going in and out of the finals and conference finals since the late 90's now and in a highly competitive Western Conference . His superstars are all past their prime but hes found a way to bring in younger guys and role players and get the absolute most out of all of them. I think it's amazing. All his older stars never go over 30 minutes ago, something Doc could never accomplish here.
And yes, Phils teams have beat Pops teams in the past, but as far as longevity goes, theres something to be said about a coach that has the balls to stick around and work it out to keep his team elite when it looks like his superstars are past their prime. Not run away and retire.