Lord of the Rings

[The Artist Formerly Known as Hawk]

You seem to be forgeting that LotRs started as a book. Which was a sequel to another book (wherin, incidentally, Sauron was working behind the scenes and kept Gandalf busy so he wasn't around to save the day every 5 minutes, which would have led to a more boring book right there), as well as all of the stuff in the Silmarillion which was being dreamt up at the same time in which Sauron plays a big part as second in command to the first evil lord of earth and was directly responsible for leading most of his armies into battle.

He also later took over Melkors role, corrupted men and Dwarves, nearly fucked over the Elves, destroyed the greatest race of humans ever and indirectly caused the world to become round!

So actually, when you consider the massively complex and detailed backstory for the whole universe, Sauron is pretty fucking important and his role in LotR makes perfect sense and wouldn't make sense if he suddenly wasn't there.