The OP states that the match is Tony vs Thanos not Genie vs Thanos. Genie wouldn't just be attacking Thanos, he would be responding to Tony's commands (wishes). In the movie it is stated that the lamp wielder must rub the lamp while stating their desire in the form of a wish (i.e. I wish Thanos was dead). In addition to that, Genie doesn't just blink the wish into existence. He rolls his arms around and builds up to it.
Before all that happens, Thanos could easily snap, blast, transmute or any number of things to defeat/kill Tony. To me this fight is a quickdraw and in that, Thanos has a major advantage