Well, you do have to draw the line between appearance and functionality at some point. The entire way the game works is using a volumetric system over a vast area. For enough detail to satisfy the visual junkies, you'd need a game that would not run on any computer currently available, Java or not.
I hate to drag up Dwarf Fortress again, but I think it's worth a mention, because it's an example of how the richness of the gaming experience is not neccesarily dependent on the richness of the visual experience. It's, in part, down to the player as to how enjoyable that experience is, there's nothing wrong with a visual tour-de-force but there's always a trade off between aesthetics and diversity.