Joshua Tree-secular, Still huge seller but I have sooooooo many....80's music rules! Or maybe I am just old.
Jesus Freak-religious, Mainstreamed christian rock in a lot of chruchs
Moonlight Sonata (piece not album)-classical, I actually hated classical growing up but this piece kills me.
Grease. To each his own. I just wish I had the hair left on my head to use some grease.
Got to be Pink Floyd's The Wall
FRANCES THE MUTE by mars volta
Guns n Roses' Use Your Illusion... As a whole, both albums dug deep into their repertoire, from before Appetite for Destruction. It also was very diverse. I also treasure Nine Inch Nails' The Fragile, another double album or disc. I also like The Eagles' Long Road out of Eden double-disc. I am a big fan of the double-disc as long as the material is worthy of being on a single disc release format and not obvious fill-in material. I mean for example, Tupac's posthumous release of a double cd a few years back signifies the wealth of material an artist has, or in Tupac's case had and is now in possession of his mother. Pink Floyd's The Wall is great, but in my opinion it has what I would call "fill-in" material...
Fill in? The wall? Oy! You'll be dissing grease next. Hehe, I was always a double fan too. Like Kiss- Double Platnum
No no ! I like Grease !
I dont care, I'm saying it: The soundtrack to GREASE
Tell me more tell me more 
FRANCES THE MUTE by mars volta
Probably this one, or something by Toby Driver, John Zorn or Björk.
Too many to mention, really.
EDIT: Grandeur of Hair by the Goslings!!!
BTW--Dark Side of the Moon, Pink Floyd longest/highest charted selling album of all time!
While I like Dark Side of the Moon, sales numbers do not necessarily point to an album being good, Britney Spears had good sales numbers and she's awful. As for best ablum ever, I like "concept albums", where the whole album/CD has a goal or theme, it's more than a buch of songs thrown together. If you ask me this question again in six months, I might have a different answer, but right now, and to throw out something different, how about "In the Aeroplane Over the Sea" by Neutral Milk Hotel.
Zepplin - Led Zepplin or ZOSO
Supertramp - Paris
ELO - Out Of The Blue
BS - Born In The USA
Beach Boys - Pet Sounds
That's just to name a few and totally depends upon the mood i'm in.
For best single... I really like Viva la Vida by Coldplay
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To many to list but for the moment?
Radiohead KidA