This is so true, but that said, when it comes to thinking about games that are visually stunning I think it has more to do with how the visual make me feel rather than simply how technically brilliant the visuals are or were at the time.
There are a few games that spring to mind for me, games like the Alan Wake series were stunning because of the way they used light and dark, the spectacular backdrops and awesome locations.
I really like the settings in the Battlefield games a lot more than the COD games as these have massive vistas and open horizons to look across.
If I had to name a single game it would have to be Assassin's Creed. From the very first time I climbed a tower and activated the Eagle Vision and was rewarded with that awesome animation as the newly unlocked map locations were revealed to me I was instantly hooked on that game. Later games improved the visual quality, but none have managed to match that moment of amazement for me in quite the same way, but I have still never tired of that and love climbing the towers in games now, be an Assassin's Creed title, Far Cry 3 or 4 or even Tomb Raider.