@croydon - The problem with video games at a party is that so many of them are designed so that only a couple of people can play. At least if you're showing a film, everyone will be able to watch it. There are quite a few lovely cinemas around that are organized so that the seating is informal and you can rent out the space for a party. They will often even do the catering for you.
Another option is to hire or borrow a projector from someone. If you've got a large, blank area of wall space you can set up a room very nicely so it seems like a movie theater.
Or you can just go with the theme and not show a film at all.