Serena Williams played her last match a couple weeks ago. Today my favorite tennis player of the modern era announced his retirement. When he was in his prime, I think he was the greatest ever. Classiest as well. At 41, if he were healthy I think he could still win a grand slam. Unlike Novak Djokovic and Nick Kyrgios he's a true gentleman.
He was great. I don't know who I would choose as best that I've seen. While I played in college (JV), I really liked Ivan Lendl (when he was on, and not pissed off and allowing his emotions to control him, he was great). Federer is definitely one of the greats of all time.
Laver was unbeatable back in the 60s, so he deserves consideration. People forget how great Pete Sampras was. Borg too. Federer, Nadal and Djokovic are all great. Roger in his prime was the greatest imo.