How are 'Best Of' compilation albums mastered?

Most of us have at least one 'Best Of' compilation albums on vinyl and the quality varies from abysmal to superb (Elvis 30 #1 Hits).
It's hard to imagine any of these being cut from the original Master Tapes....but how many 'dub' generations away from the Master is it usual to get?
And how are they assembled?

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From my experience the bulk of "best of' compilations go for quantity over quality. Too many tracks per side, thus compressed. My general rule of thumb is - at least on vinyl - stay away from artist comps.

Compilations usually good on cd and lesser quality than originals on vinyl historically.   Maybe new vinyl compilations are better but yes quantity usually reduces quality with vinyl in that more modulation in groves means less time per side usually.  
the easy way to create a compilation is to digitise everything.
an exception is paul simon's negotiations and love songs.
engineer roy halee hand assembled all the cuts in analogue, the result is a superb sounding set that often sounds better than the original presentations.
other great sounding complilations include the eagles - their greatest hits 1971-1975, steely dan greatest hits.
nb. only in their original releases, newer re-issues generally do not sound as good.
Good info audio_d...
I'm trying to wrap my brain around Roy Halee assembling all the cuts in analogue for Paul Simon's compilation album...
Does that mean the record company physically let him have the original master tapes of all Simon's albums?
And if they did....was it all at the one time or individually?