I agree with James McMurtry as a writer of great lyrics, although one would have to quote the entire song to fully appreciate the lyrics. His are not one-liner lyrics.
Greg Brown also writes great lyrics, again not one-liners and a couple of songs off his Poet's Game album are incredibly good. The title track about the power of words and the ultimate futility of words is particularly good in the context of current events. Another song on this album called "Brand New Dodge" describes a young boy riding in the new family car--a '64 Dodge they bought in November of '63. It describes the innocence that of that time that is about to be shattered by the Kennedy assassination. The only mention of Kennedy is the boy's description of the people he thinks Jesus loves which includes "And Jesus loves our president, even though he is a Catholic." Actually, there is a one-liner from a song called "Jesus & Elvis" on the same album that describes the two miracle workers; the song opens with "Jesus had some water, said "wine would be better yet, Elvis picked up a guitar and made all the women wet."