I shot this image of the Hyatt Regency Bali back in 2004 with a Canon 1Ds (11mp). My client's ad agency cropped in about 50% and blew it up to about 6' for this billboard inside Chicago's O'Hare airport. (That's me, the 5' 11" dark shadow, standing next to it.) It looked good from about 3 feet away and looked great from 5 feet or more. Kudos to Cramer-Krasselt for knowing what to do with this one.
If you're an amateur photographer, you know how important megapixels are. If you're a professional photographer, you know how the chip, lens, aperture, tripod, RAW file processing and color space all play a more important role in the quality of the image. Once you've got a decent amount of pixels to start with, the rest is up to the skill of the Photoshopper.
My point is, that if you know what you're doing with an image, size (megapixels) doesn't matter as much as other things. Some might argue that film was better because you can just do a larger scan. Not true. Film also had a finite amount of resolution and after about 80mb, a scan would only show more grain, not more image quality.