A toss up between Gonzo and Massu I guess, depending on whether you think a slam final or a gold medal in singles is a bigger achievement.
That's how I see it. Massu is probably the least talented of this group but two Olympic Gold Medals is huge especially when your country had never previously even won a single gold medal.
At first because of Massu's gold medal I veered to selecting him. But as Gonzalez also shared the doubles gold medal plus he has the slam final, a lot of titles and a top 5 high ranking I think I would give Gonzo the edge. Oh yes, and Gonzo is ten times more talented than Massu too for what it's worth.
Ferrer in current form has a good shot at moving up this list however. It is pretty close between 3 and 6.