I agree with Happiness being some sort of/something close to a masterpiece. Roger Ebert summed it up very well.
"...the depraved are only seeking what we all seek, but with a lack of ordinary moral vision...In a film that looks into the abyss of human despair, there is the horrifying suggestion that these characters may not be grotesque exceptions, but may in fact be part of the mainstream of humanity... It is not a film for most people. It is certainly for adults only. But it shows Todd Solondz as a filmmaker who deserves attention, who hears the unhappiness in the air and seeks its sources."