Agassi wasnt dominant since there were people better than him on every surface.
Carpet- Becker, Edberg, Sampras, maybe Ivanisevic and Krajicek
Grass- Sampras, Becker, Ivanisevic, Edberg, maybe Stich
Clay- Muster, Courier, Bruguera, Kuerten, possibly Moya
Like I said it would be one thing if Agassi was doing so great on all slow surfaces the way Sampras was on "his surfaces" as you put it, but that is far from the case. His clay court record is just better than Sampras's, but nothing remarkable by any stretch. The big dogs of clay of the Sampras-Agassi era ruled over Agassi there the same way Sampras ruled over him on all but the slow surfaces. Sampras's rebound ace record is better than Agassi's clay court record, and was even better than Agassi's rebound ace record until Agassi was in his 30s, so how can Agassi be called some slow court king on a par with Sampras on faster surfaces. And Sampras on rebound ace was probably better than Agassi on any faster surface, certainly much better than Agassi on either grass or carpet per say.
And on hard courts Sampras was by far the dominant force period throughout his prime of 93-99. He of course won 5 U.S Opens during that time while Agassi won 2 (the latter being when Sampras got hurt and had to withdraw last moment in a year he as a lock), and even 2 Australian Opens to Agassi's 1. Agassi made his hay in many ways as Sampras was on the way down and he was having his late career surge during a weak interim era. That is when he padded his stats with alot of extra Aussies and Masters titles on hard courts.
So Sampras was only dominant on half the surfaces. Agassi wasnt dominant on any surface other than maybe rebound ace in his 30s vs one of the worst fields in history. So of the two Sampras is by far the more dominant.
To put it in the simplest terms possible Agassi arguably wasnt the best player in the World at any point in time. The only time he might have been was 1999 but even then he had the asterix of Sampras's last minute U.S Open withdrawal and his 1-4 head to head vs Pete that year. And Agassi was never the best player in the World on any surface for any sustained period other than rebound ace from ages 29-32 after the Sampras era had ended and we were in an interim era. He was never considered in general the best grass courter in the World, best clay courter in the World, best carpet player in the World, probably ever even the best decoturf player in the World. Even when he won his lone Wimbledon and his lone French Open I dont think anyone considered him the best player in the World or the guy to beat on those surfaces. Sampras atleast was for many years considered the best grass court, best carpet or indoor, and best decoturf player in the World.
Finally, someone talking some sense. Agassi is the most overrated player. Him and Sampras are not even in the same league. The only reason Agassi is this liked is because of his personality and Americans liked that, that's it. Agassi is not even in the top 5 best tennis players.
