Agassi has the best return ever. He is also probably the cleanest ball-striker.
His only flaw was his defence and maybe his net game.
His return wasn't that great against Sampras. Yes, Andre was a great player and would do well in today's game, but so would Sampras. Why wouldn't Pet's game benefit from today's rackets? The fact is it has, he has said that he should have changed his rackets before he retired. His backhand is better and more consistant today than in his prime. The fact is that just because Agassi was lucky to win 1 FO and 1 Wimbledon, Pete was the superior player with far superior stats than Andre's. Pete, Roger and Novak, not necessarily in that order, would be the top players today if all were in their prime. Nadal would be the top player on clay, Andre would be #4 on hard courts and grass.