I think I agree with excluding greatest hits (except, as mentioned in another discussion, for artists from the time before albums were really a thing, like Robert Johnson), but I don't agree with excluding live albums and I'm on the fence about the other two. The O Brother Where Art Thou? soundtrack is 100% its own thing and should be eligible, and excluding live albums would eliminate, for example, Neil Young's Time Fades Away, which features almost exclusively unreleased material, and the recent N&G AOTM, 15-60-75 (The Numbers Band)'s Jimmy Bell's Still in Town.