I would definitely say Wang Liqin is my favorite player of all time. He has kept himself in insane shape for more than a decade, that shows an amount of discipline that I really haven't seen in any other player. He has an amazingly powerful forehand, but in addition to that you can just tell from watching him play that his brain is always working, he varies it up and plays very smartly. His serve was never his strength, so he always depended heavily on just playing the rest of the point good. If the point got past the first 3-4 hits, his percentage to win was probably the highest of any player, and the longer the match went on the better he adapted and the better he got.
In my opinion he had the ultimate mix of skill/athletic ability. No one who was taller than him was even close to as fast and quick as him, while no one shorter than him had his long reach. Xu Xin is able to probably match him now, but before that, if you compare him to people like Samsonov, Wang Liqin's speed and reaction rate, makes Samsonov look like he is a 60 year old man.
I also really like Ma Lin because I just love his style. Though he uses the reverse bh now a decent amount, his play style still revolves around the old penhold style, of having an amazing serve, controlling the short game perfectly, and then being the first attack, and ending the point within the first few hits. Its a style we are seeing less and less of, because its so hard to master and requires a lot more footwork and movement than shakehand, but its still so fun to watch, and Ma Lin epitomizes that style.
As for the new generation, its hard not to say Ma Long, because he is just relentless, overpowering, and has very few if any real weaknesses, though I do have to say that he is pushing the speed of his game to a level that is so fast, that a good blocker might be able to have an advantage against him. He is able to attack and loop everything so quickly, but its creating so much speed that its not giving him a great chance to recover if the ball comes back. His game against that Chan player, that Chinese player who plays for the Japanese team was a good example, though I do realize that Ma Long was recovering from an injury that game.
Xu Xin is pretty fun to watch, he has a lot of potential, his forehand is amazing, and gets some insane angles both because he uses penhold, and because he has the height.
While I don't like Zhang Jike's attitude, his play style is pretty amazing, his loops from both back hand and forehand have like the perfect arc to them.