If you're new to this series, start with Volume 5. It's the most entertaining of all, and it will be the best gauge for you to decide if you'd like to expand your collection with volumes 1 through 4. Volume 1 is no slouch, but from the very beginning ("Chuck" Heston explaining the MPAA rating system while playing tennis) Volume 5 is pure entertainment.

Another bonus is that the trailers are clustered together by genre; so, for example, if you don't like the Kung fu trailers, you can just skip ahead a few chapters and you'll be on to new territory.