I am curious , I've tried many games , Ground Zeroes, Skyrim , The Batman Games , the only game that had somewhat of a big difference is Tomb Raider , but thats mainly due to TressFx making the character model look better , the actual environments don't really improve significantly.
The reason I ask this question is I remember CD Projekt Red saying that the Ultra settings for their game was very different from 'High' or to that effect. Obviously it wasn't true , but are there games that do show great differences?