Concentrating on sublime Beethoven seems snooty, like insisting on premier cru claret. But the truth is that this music isn't just better than that of the earlier periods. It initiates us into a new musical order in which melodies sound like divine improvisation, though in fact they are undergirded by the tightest counterpoint since Bach.
As Edmund Morris points out, Beethoven's climaxes are created contrapuntally: the wildest of all, in which violins, viola and cello squawk and scream like frenzied vultures, occur in a fugue - the Grosse Fuge of the String Quartet Op.130.
The late sonatas are almost hypnotic in their power. My favorite recordings of the late sonatas (say op109 tp 111) are Schnabel, Ashkenazy,Kempf, and Gilels.