The Chosen 1
I always thought Palpatine knew of the Jedi Chosen One Prophecy so he wanted Anakin as his apprentice to prevent it from coming true, thus preventing his own destruction. Later, he saw an opportunity to do the same shyt with Luke and had no problem tossing toasted Vader in the bushes.
I don't know if he necessarily believed in the prophecy...otherwise he could've just killed Anakin.
To be honest I think he just wanted Anakin because of his high midichlorian count. The Sith always want the strongest apprentice possible.