I am half reminded of the Chinese unlicensed SNES/genesis titles at this point.
There was some talk about moving the DS copies of various final fantasy games from the DS 3d to the DS 2d graphics (DS 3d is rarely pretty and GBA/DS 2D is probably about as good as it gets, certainly more than capable of whatever home consoles could have ever done).
Some Zelda games have had discussion towards this end though this is usually for people that started out on other titles and want the SNES Link sprite changed to one they are more familiar with (I have met it several times for the GBA port).
I think some of the fire emblem crowd have done something here though that is often more for games of a similar generation or using old characters or something.
Straight up demakes though usually come in the way of fan games and homages which in turn tend not to be made for the old consoles and especially not as hacks (homebrew games being the case here). Similarly I have never seen the logic really applied to making 16 bit era looking games look like 8 bit era games. Granted I have probably now made a comment like I see when others say things like "old consoles like the N64"... relevant XKCD http://xkcd.com/771/
There is also the likes of FF7 NES I suppose ( http://www.romhacking.net/forum/index.php?topic=12466.0
) but that is an unlicensed title (though I practice I reckon homebrew is probably a better term) and back where I started.