It has been a tough couple of years for drummers, hasn't it?
Well, I think to be the best living drummer, being living is a fairly firm prerequisite. I'm honestly not sure who I'd nominate in this category.
However, best of all time lifts that restriction and opens the balloting up to some of my favorites. The late Neil Peart comes to mind as having it all, always on time but absolutely able to bring the fireworks. The late Charlie Watts gets my vote as the always just right drummer, perfectly on time, never too much, and never too little.