I think gaming in general would greatly improve if developers focussed more on atmosphere and gameplay than realism and graphics.
I do not think that one ideal game can exist, as different genres vary greatly; in strategy, developers often strive for greater and greater complexity, sometimes not concentrating on the concept and basis of the game enough.
In roleplaying games, less hack&slay and more roleplaying in the original meaning of the world should be involved.
Shooters... well, the reason I've never been a fan of that genre is the often-repetitive gameplay. I know there are expections, and half-shooter games, some of which might interest me.
Other than that... the adventure genre has no great problems currently in my opinion, and racing is not my thing, but some racing games currently are quite good.
These were, of course, only examples, and I overlooked many genres. In conclusion, I think a game cannot be ideal as such, but wjile developing a game, one should have good basics first, and then add complexity, graphics etc. Usually, realism should be less important than gameplay, with a few exceptions, such as certain simulation games.