Rubnstein's are beautiful - both his early and late nocturne recordings. Cortot and Arrau are also superb.
Pollini is pretty bland and uncreative. There are much more interesting interpreters. Ashkenazy is ok. Pires is adventurous and worth listening to, but a bit over-the-top at times.
Honourable mentions:
Hofmann's numerous recordings of 9/2, 15/2, 27/2 (Marston Vol 5) from the mid-1930s all exhibit mesmerizing virtuosity and stunning individuality.
Friedman's 55/2. One of the greatest nocturne recordings ever made. Rubinstein's sounds lacking when compared side-by-side! Horowitz's late recording is comparably moving.
Moiseiwitsch: 9/2, 37/2, 62/2, 72/1 (spread over a couple decades and many releases). Huge shame that he didn't do a full set!