In RotS, when Palpatine is inducting Anakin into the Sith (after the Windu duel) Anakin asks him to help save Padme. Palpatine says "to cheat death is something only one has achieved." We know from his Darth Plagueis story that Plagueis could create life, but specifically did NOT cheat death.

I think Palpatine was actually referencing another character-- Darth Revan himself.

(KotOR spoilers)

Revan was presumed dead by almost everyone at the beginning of Knights of the Old Republic-- his entire memory had been wiped and he was allowed to assume a new identity. However, even after that, when Revan has become a totally neutral/light side and enigmatic character in the universe, in SWtOR the MMO, he is still alive in some way.

Palpatine was referencing Revan, who cheated death through the Force, but told Anakin the Plagueis story because he does not want him to know that one can only become immortal through through the light side of the force, as Yoda and Obi-Wan do.

Maybe Anakin figures this out through his apprenticeship as Vader. After all, he does end up a Force ghost.