As I said elsewhere: soundtracks should establish & enhance the atmosphere, aid in telling the story, and also be fitting to the setting & gameplay. Not be merely ambient noise that barely makes itself known (unless it’s fitting to do so). Bonus points for notable variety in genres & style whilst following these rules, much like System Shock 2 or Deus Ex.
I’m fine with ambient in moderation, but a pure ambient focus is underwhelming for me. There’s only one game with an ambient-only soundtrack with composition that I am fond of and that is Arx Fatalis’. I don’t know why that is, the sounds just resonate with me I guess, or other games that focus on ambiance do it wrong.
System Shock 2’s soundtrack is near perfection for me. The Jungle/Drum & Bass provides an unsettling sense of technophobia, and gets your blood pumping. A lot of the time they play during combat-heavy sections (engineering tubes & escape pod bays), so therefore are fitting to the situation at hand. It also helps that the majority of tracks are just enjoyable (in my opinion). The ambient, well you know what that does, and it also does it very well.
This variety simply makes SS2 a more interesting and enjoyable game, for me. Less is not always more.
I’m so very tired of modern snoozefests, even if they are poor examples of ambiance. Bring back the old ways.
Also it’s interesting to note that you named yourself “dnbguy” yet seemingly want to remove the dnb from System Shock.