I'm not sure whether it's the best, but by far the most famous hotel in Havana is the Hotel Nacional.
Located in Verdado, the centre of Havana, the hotel overlooks the Malecon, the famous sea wall where you will see the locals hanging out and swimming during the day.
The hotel opened in 1930 and was initially a hit with the Hollywood stars and other celebrities of the day including Johny Weissmuller, Buster Keaton, Jose Mujica, Jorge Negrete, Agustin Lara, Tyrone Power, Romulo Gallegos, Errol Flyn, Marlon Brando and Ernest Hemingway.
Other notable guests include Winston Churchill, Alexander Fleming, the Duke and Duchess of Windsor and numerous shady mafia characters.
Today, the hotel still keeps much of it's grandeur and is definitely worth a visit; however, it's questionable whether the actual hotel rooms and service received are worth the premium paid to stay here.