It's quite funny that a lot of ambient artist in the 90's would see their album as new age, i.e. by Robert Rich but also more underground artists, and that is is now rarely used, and if so, mostly in a dismissive manner.
Anyway, I like quite some ambient but most of the time I go for something more active. I don't think there is an 'ultimate' ambient album or that the genre has to 'sound so and so', that's an absurd statement. What I do like is what I am listening now, Radikale Akzeptanz from Belia Winewisser, which offers a lot of different sounds and structures. Not all ambient per se, there are some tracks one could say are more IDM-ish or techno-lite, a varied piece of work but overall encompassing it really is an ambient album. Varied, but still very much within the theme.
But I also really like more glacier/'pure' ambient albums as something from I.Corax (who remembers them?) or drone pieces like the Organum works.
And what about Altar of Flies or artists that uses a lot of ambient set an atmosphere in between tracks or as transitional pieces?
(Previously I posted something dismissive about those that dislike ambient but do like it when made by black metal artist, and however I still think it's an strange way at looking at things, I really worded it too strongly)