Some of the issue with games is optimisation. The original Ryzen only came out two years ago this February. Considering most triple A games take 2 or 3 years to make, every new game released today was started prior to Ryzen's debut so any changes for AMD had to be added in as an afterthought.
It's not only a case of games optimisation, it very heavily revolves around Windows Schedular as well. Until Microsoft actually give AMD a level playing field on that count, whatever little games devs do will mean next to nothing.