I put a lot of hours into Skyrim to the point where I think I hated the sound track, it felt so repetitive. That said, the amount of time I've spent at the Firelink Shrine just standing around is probably worse.
To me they're both excellent but both add to the game differently. Skyrim seems to add to the atmosphere with music, whereas Dark Souls adds to it by the lack of audio. It definitely wouldn't have made as good an impression on me if it was constantly on in the background. Then those moments happen where you spot your foe, he's 100 times your size and the audio cranks up and just makes it an epic, memorable fight.
Unfortunately I've owned Demon Souls for years and never got around to putting a decent amount of time into it. The nexus sounded great, but I can't vouch for any other areas. I really must get around to finishing it.
Currently playing: Ni No Kuni, DayZ and Dark Souls.