Leave Sauron to me was a great line.
Yep. That's the type of thing the SW prequels should have done. Little moments, even entire battles that are connected to the previous trilogy but that don't ruin or spoil upcoming events. "Leave Sauron to me" is only ominous if you know what he's going to do in FOTR but someone can still watch BOTFA and then FOTR and still be surprised when Saruman turns against Gandalf.
As opposed to watching the SW PT which outright spoils all the major twists (Anakin is Vader, Vader is Luke's father, Luke and Leia are twins) of the OT.