Double Albums/CDs, curse or blessing?

For no good reason, I have been thinking about the worth of double albums or cds that bands release. The only two that I can come up that make sense are the Who's Tommy and Pink Floyd's The Wall. These are obviously rock opera type albums that hang together. Excluding Greatest Hits which might make sense, are there others doubles that people think of highly?

Most other double albums (double cds more so) I am familiar with would have been much better if only the best material had made it onto a single disc. Examples in my view would be Red Hot Chili Peppers Stadium Arcadium, Guns N Roses Use Your Illusion I & II (at least they are sold separately).

While it may make the bands more money to issue doubles, I think that it generally cheapens the brand.

What do fellow agoners think?