If you are going to watch the PT(which I am not a huge fan of), I'd recommend this order, and you keep all the suprises intact:

Star Wars

Empire Strikes Back

Return of the Jedi (stop right after Obiwan talks to Luke on Dagobah)

The Phantom Menace

Attack of the Clones

Revenge of the Sith

Return of the Jedi (continue on as Luke meets up with the Rebel Fleet)

My reasoning is that you watch SW & ESB and it still keeps the freshness of the original movie without the tainting of the 'saga', ESB is preserved because of Vaders revelation. The first part of Jedi is all about saving Han, so it keeps the story intact. Once Luke talks with Obiwan about Anakin, it is then like a huge flashback (TPM, AOTC, ROTS), and then resumes with the final part of Jedi with Luke, Vader, and the Emperor in the throne room, and the rebels trying to save the galaxy.