For me it was Mafia 2 in 2010. At the beginning of the game it takes place in WW2 and you were running through some historic building or something and there was so much detail (for the time) and I was thinking damn they put so much work into this just to force the player to run through in mere seconds and not have time to appreciate all the little details.
In those years (2009-2011) my brain had to adjust to the modern games because there was so much little details everywhere that I wanted to stop at each table for example to check if there was anything useful on it or it was all junk.
Now I recently upgraded my grafix card to play everything on ultra at 1440p but I keep coming back to PS3, currently playing Uncharted 2 which is 10 years old now but looks so good.
Deus Ex (2000) - a game that pushes the boundaries of what the video game medium is capable of to a degree unmatched to this very day.
