I know some people say Murray - but I go with Miloslav Mecir. When you say him play, well he just made some elite players look amateurish. Wonderful hands, anticipation, ability to change direction, disguise. He won the WCT Finals which was a very big tournament, Miami (when it was regarded as the 5th slam at the time and was best of 5 sets every round) and got Olympic Gold. He also was in the US open final and Australian Open final (lost both to Lendl - no shame in that). He also was dominating Edberg for 1/2 their Wimbledon Semi-final in 1988 before Edberg came alive, even though Mecir had a back brace on. Edberg went onto win the title. I believe if Mecir had got past Edberg he would have beaten Becker in the final. I don't know of another player who could make as strong a case (except perhaps Murray - but Mecir was a far more talented player).