Take Uru as an example. Nobody was happy with this 3d non-photorealistic puzzlegame variant of Myst, but it was still beautiful. They made a whole MMORPG out of it with various ages, lands and since it's only about exploring and finding new stunning areas, the focus was on the level design.
I always thought that the old Runescape(not the new hd version),had rubbish graphix, but it is stil very popular!
