It depends on what you're into. When was the last time you've seen a Star Wars movie? If you're a big fan, even a fanboy, then you wouldn't have any trouble deciding. On that note, I'd say go see Spiderman first because of the lines, then sometime in the next few weeks watch all the Star Wars movies and then go to Episode II, you'll enjoy it much more than if it's the first Star Wars movie you've seen.