I don't think that simplicity is the main key to the success of the oldies. 3D is not from the devil, but it really hijacked the evolution of games. With the extreme level of graphic there's no room left for imagination. This leads to futile emotional binding towards the game, at least for time-worn gamers like myself. I feel myself an observer of a new game not as a "part" of the adventure.
Fortunately, I am as an isometric junkie coding in a parallel dimension where no 3D break-throught happend. :) I found myself developing a 3D browser game with 2D graphic. If you are interested in such a hybrid try it here: http://toborzsokinteractive.blogspot.hu/