Probably not, no, but that doesn't take away from some of his remarkable accomplishments. to me the most impressive is his Slam-winning span of 20 years: his first at 18, last at 37. Pancho, Hoad, Laver, and Connors were all better in their primes, but Muscles was right there for all of them.
Overall I think Rosewall is historically underrated, because of the "Slam Title Fallacy" (which I would define as "the reduction of a player's greatness to their Slam title count"). He's definitely top ten in my book. In fact, the only three players I'm comfortable saying were greater are the "Three Rs": Rod, Roger, and Rafa. Ken's in the mix for #4 along with Tilden, Gonzales, Sampras, and Novak.