OK Computer always tops these sort of lists. Personally I doubt that it's because it's the best album ever; more because Radiohead fans seem to be rabidly obsessed by the album.
Most of these lists are a bit of a sham, because there are numerous albums that always appear in the list:
The Beatles- Revolver, Sgt. Pepper, Abbey Road.
Nirvana- Nevermind.
R.E.M.- Automatic For The People.
Beck- Odelay.
Primal Scream- Screamadelica.
Public Enemy- It Takes A Nation Of...
U2- The Joshua Tree, (occ.) Achtung Baby.
Oasis- What's The Story..., Definitely Maybe.
Pink Floyd- Dark Side Of The Moon.
The Sex Pistols- Never Mind The ********.
Blur- Parklife.
Radiohead- OK Computer, The Bends.
That's 17 albums off the top of my head (there's probably 17 more) that always appear, not because they're good (although some of them are) but because they're a safe option. Oh well.