Part of what I've always loved about TES is that I can play it without speakers. In fact, currently my computer has no speakers. I have headphones that I put on when strictly necessary, but mostly I just turn on my subtitles and read. I actually hate voice acting, always have. I'm too bloody impatient for it. I don't need sound.
Don't care about load-times either. I keep a book on my desk specifically to entertain me while things are loading. Works well.
Everything else is important though, and hard to sacrifice.
I chose Atmosphere first, and Lighting second.
Lighting is important. I'm increasingly looking at OB, and realising that what I find attractive/unattractive almost always comes down to lighting in that game. (And I find parts of it
remarkably unattractive.)
Atmosphere is most important to me though, mostly because I like getting lost and gogging. That's... yeah. That's what I do most. So pretty things that fit together and make the world feel real are important to me. I missed seasons so much in the DF->MW switch. So. Much. It just didn't feel real to have the season be winter, or fall, and to know that from the month, and see no indicator to that effect in-game.
Of the others... Detail would be my third. Because it adds to atmosphere, really.
NPCs and interactivity... I don't know. Interactivity is a moot point in a lot of ways for me. If it's something I can't think of a good RP reason to do, my character won't do it. Period. So the inability to actually do so in-game never really hurts me at all. It's
nice, but by no means necessary for how I play.
NPCs... I dunno. Anything above sprite-level
still strikes me as amazing, so I'm not one to ask.