In my opinion the one key element that makes any game great is the A.I. behind the in-game characters. For an environment to simulate reality you must first make the humanoid characters simulate real humans!
Some great examples of games with stellar Artificial intelligence simulators are:
      The Halo Series.             https://www.halowaypoint.com/en-us
            This series will go down in history for making the biggest "splash" in video game history. While the earlier games were graphically on par with most of the games coming out at the time, the game itself immersed the user in an alien infested planet where he/she was the final hope for mankind's survival. I love this series b/c as the games progressed they added more and more features to the game while keeping in line with style and feel of the previous games. Specifically the grunt AI's were the best because they at some point would decide to just give up on fighting and would rush straight at the humans with grenades ready to go off. Perfect for making the game feel real.
 
      Hitman: Blood Money.   https://en.wikipedia.org/wiki/Hitman:_Blood_Money
            While this game was not very popular by any means i still hold this to be amongst my favorite console games. The reason being is because the level of detail that you as the user have to pay attention to is honestly astounding. If you need to get around a corner and there is a guard blocking the way you must think on your feet in order to get around him by either tackling the guard head on (and risk alerting the whole area) or you can be slick and divert his attention for long enough to get past that area. I'm extremely excited for the new Hitman game to come out because i know it will not disappoint.