Zedd was the top dog in quality 2 years ago, he has lowered his quality to appeal the masses and that's so so sad, is not because he is working with pop girls now, but the reason is the quality of Break Free and specially IWYTK has been dropped in an extreme way from his former tracks. It's so sad to see.
I would have said Zedd but after the poor vocal choices of IWYTK it made me see that Calvin is the one on top. He not only knows how to make amazing beats but he knows just what vocals are perfect for the song.
Tiesto is the only answer honestly. His sound is just IMMACULATE for years now
After him- I'll go with David Guetta (people wanna hate on him but he WAS a force and still makes amazing dance tracks) and Dillion Francis (should be more famous!)