Look at the Coen brothers. All their minor characters are as interesting as their protagonists. If the smaller characters are well-written, the whole world of the film becomes enriched. It's not the size of the thing, but the detail.
“We often plough so much energy into the big picture, we forget the pixels.”
“At the first screening, there were a lot of areas that we went around and around about. Then we had our second screening. It played better. It's almost a reasonable length film now!”