Graphics and graphical effects, combined with sound and physics, is what makes me really enjoy playing a game. I don't even need to do anything. I can just prance around like a moron shooting the wall.
For me, they are very important. But obviously they don't matter if the rest of the game is complete crap. As someone mentioned earlier (fantastic point, btw), it depends on what kind of game it is. I would never enjoy a FPS or 3PS if it had horrible graphics. I could, however, enjoy a strategy game even though it would have crap graphics. Case in point, Warcraft 3's DotA map. That doesn't mean graphics in a strategy based game aren't important. The only reason me and my friend play Supreme Commander 2, besides being a good co-op strategy game, is because of the most fantastic large battles that occur. It's such a thrill to see a large scale battle with great graphics and graphical effects.
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Anyways, go Bethesda for putting emphasis on immersive (why isn't that a correct form of the word btw?!) mechanics such as graphics.