Oh gosh, this is so tough. There have been so many excellent players on hard courts over the years.
Certainly the players General Hercules has listed belong near the top, especially in recent times.
But I would have to include Jimmy Connors, Rod Laver, Richard "Pancho" Gonzales, John McEnroe, Andre Agassi, Stefan Edberg. The two Andys, Roddick and Murray are not far from those, and with Murray still active, he could still rise to that level.
Respectfully,
masterclass