For me its without a question Ma Lin. For me, he epitomizes all the great strengths of the penhold style. Better serves, better forehands, with greater versatility, way better short game. I don't think anyone in the modern game has a better control of the first three balls, and has mastered the three ball attack better than Ma Lin. Wang Hao has brought the penhold style to a new different level by using the RPH which is a great advantage, and if done right erases just about all backhand disadvantages of the penhold style, but in terms of serving, short game control, forehand versatility, he pales in comparison with Ma Lin, and its why in their games against one another, Ma Lin still wins a lot more, despite having an plainly inferior backhand. The Chinese coaches say that in terms of the three areas of table tennis, spin, speed, and power, Ma Lin's game has the most spin of anyone in history. In the interview with Werner Schlager, which is in another thread, there is a reason why despite him saying Wang Hao has really good skills, the player he feels has the most technical potential and technical skill is Ma Lin. He could have been scary good if he had been trained from the beginning with the RPH style. He is getting old, but during the period 03-06 when he was in his prime, his three ball attack style was amazing. Just watch some of his games against Boll, back then he would get almost have his points in points that didn't go beyond the 3-4th ball.
I don't think there has been anyone in the history of table tennis with a better and more versatile forehand or shortgame.