That's a very subjective question... if I had to think of a game I go back to just to "rinse my eyes" with what I consider beautiful and artful graphics, ones that give you that "I'm sitting by the fire with a blanket on and I'm cozy" feeling, for me that game would undoubtedly be Heroes of Might & Magic 2.
Devyatovskiy: The literal definition seems to correlate to graphical fidelity.
Couldn't be further from the truth. Beauty is in the eye of the beholder and some eyes like "unreal" vistas more than others. Realism doesn't equate to beauty, never has (at least not necessarily).
Strijkbout: On the other side of the spectrum there is X2, which I'm playing at the moment, the graphics still look very good in my opinion.
X2: The Threat? Well... that's the first game that introduced me to the X series, and I have to say, while I still have fond memories of it, the graphics in X3(:AP) are a big step forward in almost every regard. So much so that I don't see myself ever playing it again. The weapon effects in particular are rather hard to bear in comparison.