All of my favorites have already been mentioned, but I will say them again...
Vladimir Ashkenazy is, by far, my favorite pianist, and in my opinion (I mean no disrespect to the late Rubinstein, rest his soul), he is the authority on Chopin interpretation.
I also love Jean-Yves Thibaudet, and I first heard of him due to his playing the music to the soundtrack of Pride and Prejudice.
I also LOVE Dustin o'Halloran and George Winston, but they are more contemporary, not so much classical.
Daniel Barenboim's interpretations of the Beethoven Sonatas (Barenboim is also another favorite), cannot be matched, in my opinion, even though there are other GREAT pianists who have played them well (Wilhelm Kempff).
While I detest Lang Lang, I do enjoy Yundi Li.
Others that I'm iffy on, or just flat out do not like...
Valentina Lisitsa: I like her intepretation of Rachmaninoff, but otherwise, I feel like she's pretty much Franz Liszt on steroids.
Nikolai Lugansky: I've only ever listened to his Rachmaninoff preludes, so I can't give a very fair judgment call. I just think he's pretty, and in his younger years, I would have wanted to have his children.
Lang Lang: I cannot stand him. In all the performances I've seen of him, though he is a great pianist, I feel like he is far too showy, and he "acts" way too much. And though he is a great pianist, I do not particularly care for his interpretations.