For me, it kinda depend on whether I'm in prequel mood or not. Sometimes I watch all six and I stick to the official DVD versions but when I'm in original trilogy only mode I watch either Adywan's SW Revisited or the Lucasfilm Pwnage Edition, Adywan's ESB Theatrical Restoration, and Harmy's Jedi Theatrical Restoration.

I also some times like to watch the original Star Wars on its own without any of the sequels or prequels and imagine that Vader really did kill Luke's Father, the Emperor really was just a powerless figurehead under the influence of officials like Tarken (as the Novel prologue implies), Han used his reward to pay off Jabba right away, Luke and Leia aren't brother and sister, and the senate came back together on it's own without the Death Star to keep them in fear. It actually makes for a completely different movie experience that way.

On a side not, my favorite version of Star Wars period is the Radio Drama since it goes into so much more detail about the Empire as well as the full Biggs Darklighter subplot which I feel is sorely missed from the movie because I feel it adds so much to Luke's character and motivation. Star Wars from the Adventures of Luke Skywalker is a close second followed by the Manga adaptation.