Ok, I'll play the game.
Of what I own, what I would quite legitimately expect most middle class men of a certain age to have:
a Nick Drake album
something by Talking Heads
ChangesBowie or Ziggy Stardust
some Miles Davis
a bit of Neil Young
Forever Changes by Love
and something by the Penguin Cafe Orchestra
and if a past girlfriend was into it, Blue by Joni Mitchell...
If they were (or wanted to appear more open-minded, they might also have some old school hip hop, particularly:
A Tribe Called Quest,
De La Soul's 3ft High and Rising
something by Public Enemy
Ill Communication or Paul's Boutique by The Beastie Boys.
If they were in their musical youth in the late eighties, early nineties, they probably also have:
some trip-hop like Portishead, Massive Attack, Tricky, or Morcheeba (if their girlfriend left it with them);
perhaps Bjork's first or second album;
Pixies' Surfer Rosa;
the first Stone Roses album;
Blur's Parklife
and the first or secondOasis album.
(They probably did own some more embarassing Madchester / Britpop albums like James, The Farm, Sleeper or Echobelly, but they left them at university or something)...
and so on...