Some players of the 50s (Sedgman, Hoad, Segura) and some experts (Mezler, Flink) rank him above Gonzalez or Budge. He was one of the first, who played the Big Game. Its imo open to discussion when he did develop it, still as amateur or on the pro tour with Riggs. In clips of the 1947 Wimbledon he doesn't come to the net.
In a Tennis Magazin interview in the 80s he regretted somewhat, that he lacked a real rivalry with another great player. Budge was too old, and Gonzalez too young for him.
I have some problems with him, because imo he was very selective in his chosen play, selecting carefully his places and (fast) surfaces. He never played at RG as an amateur (Rosewall mentioned that in an interview with Eliot Berry), as a pro he chose his places on the one on one indoor series, and often skipped US pros or Wembleys. After his initial series win over Gonzalez he went out of a more experienced Gorgo's way a bit. He dominated the amateur scene, when the post War years still prevented a strong amateur field. He lost the fewest games in Wim history in 1947, but the Wim field was rather weak, while for instance the 1949 Wim field was very strong with matured players, and i would have loved to see Kramer against that kind of field (Schoeder, Sedgman, Drobny, Gonzalez, Patty, McGregor and others). He also dominated the pro scene, but it was not the class field of the later 50s or the 60s. I think, that other pro champs like Gonzalez, Rosewall or Laver put their b... more on the line over a longer period of time and on a more consistent basis.