That varies VASTLY depending on what skill you're at. At D3 where I am, I'd say maybe 2 out of 3 games have at least one person showing banners or skins that are exclusive to Grand Champ tournament winners.
this is completely ignoring the botting issue that was so bad lately it pushed pros out of ssl and severely messed up MMR. this season is the first one that is remotely playable in a while