Infinite Jest was also nominated but definitely deserved to make the cut.
Also, Kafka was robbed at thirty-whatever-it-was. Definitely one of the best closing lines of modern literature, but the Muir translation doesn't really do it justice in my opinion ("must" simply doesn't adequately render the "sollte"). For good measure, the original:
Aber an K.’s Gurgel legten sich die Hände des einen Herrn, während der andere das Messer ihm ins Herz stieß und zweimal dort drehte. Mit brechenden Augen sah noch K. wie nahe vor seinem Gesicht die Herren Wange an Wange aneinandergelehnt die Entscheidung beobachteten. "Wie ein Hund!" sagte er, es war, als sollte die Scham ihn überleben.
It's also a nice antidote to the affirmation of the other modernists on the list.
Speaking of which, the last lines of Thomas Mann's Doktor Faustus (1947) are pretty good. Here they are complete with lamentably gauche translation in a footnote.
Edit:

Originally Posted by
John B.
But that's some pretty good writing, too.
It's even better if you quote it right. It's supposed to say:
...and above the doors covered by red velvet drapes in Harry's is a sign and on the sign in letters that match the drapes' color are the words THIS IS NOT AN EXIT.