Right. Salem plays in basically an ideal fashion. He uses everything. NickRiddle, Dazwa, and Snakeee are/were all great players and I'm not saying they aren't/weren't, but Salem is, objectively, on a completely different level. The best player of a good character can do things other players of the same character can't, and until Salem's ZSS won Apex, no one completely disregarded past character experience in the manner I'm seeing now.
You can have all the Snake experience you want and still lose to Ally's Snake. You can have all the Falco experience you want and still lose to DEHF. You can have all the Diddy experience in the world and still lose to ADHD. And you can have ZSS experience as Mr. R, Otori, M2K, Kain, and Mikeneko did have and still lose to Salem because he's an incredible player that can do awesome things with the character.
Quiksilver, Nickriddle, Dakpo, V115, and Kamemushi are all good ZSS players and all of the players above had played (and in many cases, beaten!) these guys before Apex, and still lost.
Hell, Mr. R has beaten Salem, Quik, and V in tournament and seconds ZSS himself. Salem at Apex 2013 is AFAIK his first ZSS loss.