@V!ncent: Gameplay means game mechanics, it's the ease of use you, the player, have to interact with the game for example its control, logic do solve a puzzle and stuff like that. it doesn't mean that the game doesn't have 3D or a physics engine or even a good manual!
As L33F3R said, if you know how to make the perfect engine, be my guest! I would enjoy to see that! From my understanding for each genre of game there will be its own mechanics to implement. Oh if you really do create the "perfect engine" you will have to make one game from each existing genre. Here is a link to understand "game genres" but as you seems to be all knowing man i'm sure that you don't need to read it, right? check out gameplay defenition that you really don't know what it means!