it always depends on what you want to shoot.
85mm 1.8 is known for being extra sharp and an amazing lens for portraits. (but it will be a pain in the ass when you'll be in small places)
But for the style of photography i like to do.
I do everything using around 20mm to 35 mm.
I never do close up portraits (i dont do that much portraits but i love to see landscape with a person in it.)
Example (not my photo) it's from benoit paillé (Quebec/canada)
He said that he mostly use Fullframe + 35mm lens.
(Around 21mm on a crop sensor to get the same "zoom" as him on a cheaper camera)


source:
http://www.flickr.com/photos/benoitpaille/