I also want to clarify that I think Mac deserves 1983 alone not just because he beat Mats in that one match in New York, but because he won the whole Masters tournament. There was a 4-way tie in the Slams, and that leaves two ways to break the tie: the H2H between Mac and Mats, and the Masters championship, which counted back then as either the fourth or the fifth biggest tournament. When the two met in the semis, there was a lot of buzz about the match potentially settling the issue of #1, and that was true at that moment. But McEnroe went further to seal it the next day by winning the whole thing, which arguably broke the 4-way tie that there had been up to then in majors -- and that would be true whether or not he had met Wilander in New York.
A loss to Wilander in New York, I admit, would look very damaging to McEnroe, because then you'd have to consider giving Wilander a co-#1 just because he tied McEnroe in majors and was essentially the one man McEnroe could not beat in the season on fast or slow surfaces. And if Wilander had then won the whole Masters, the year would definitely go to him.
But I don't think he was good enough to beat McEnroe or Lendl on carpet. That Masters tournament, just for being on carpet, not to mention the other reasons, was a critical element in looking at the whole year.
McEnroe, meanwhile won Wimbledon, which had always carried the greatest importance; and Wilander did poorly there, again partly because he never showed he could play well on that form of grass.