Ever hear the term "patch Zerg"? Sure, there's good Zergs that have always been good like Nestea, DRG, Leenock the Ghost Slayer, and Stephano (maybe). But there are a lot of Zergs like Life, Symbol, and a lot of Zergs that just happened to get good after the queen buff.
There also have been plenty of "good" terrans who I can't even remember because they weren't anywhere near relevant after terran started to get nerfed. Player skill is a pretty dumb point when you are arguing about balance. There are enough people playing this game to get an evenish distribution of great players between the three races.
^ this. Just providing the other side to your comment, not that it isn't correct or anything Finn