For the time? A New Hope. Opens with easily the most impressive spaceship battle ever filmed, moves to an exciting battle, introduces an awesome menacing bad guy ("If this is a diplomatic ship, then where is thr ambassador? breaks neck with one hand and throws away the body) and kickstarts the plot.
I am really, really glad that someone else had said this before I got here.
The opening of ANH is a really great demonstration of minimalist storytelling. Not a moment of design - starship, character, action, nothing - is wasted; every interaction conveys something be it emotion or plot points. And after forcing the audience to sit through the opening crawl, I think that deluge of information is needed - anything less would have lost the audience.