Ask any person on the street, not necessarily a tennis fan, which tennis tournament is the most important in the world and most will say Wimbledon.
Ask any person on the street, not necessarily a tennis fan, which player has the greatest serve in history, and most will say Pete Sampras.
Whether Sampras has the greatest serve or not is debatable, I will debate it is, but it is neither here nor there anyway because the perception of the masses is that it is Sampras. If there is a perception, there has to be some truth to it. No male player in history has benefitted as much from his serve as Sampras, he was an exceptional player in any event but his whole game revolved around his serve. Everything else such as percentage of first services won or second services won is really just splitting at hairs.
First up it's Sampras.
Second up is daylight.
Thirs up is [insert anyone you care to argue for here].
That is all.