Brad Templeton's discussion of 35mm resolution has some interesting points:
Really good shots (good lens, good film, etc) will have 20 million pixels (7000 pixels across the frame), but more typical shots with a decent SLR will have resolution around 10 million pixels (5500 pixels across the frame).
Digital cameras have a contrast range of 255 to 1. Most color negative film has a contrast range of 1000 to 1. Prints have a contrast range of 100 to 1. The human eye has a contrast range of 10,000,000 to 1 (because of your iris).
Back in April I made this post on visual acuity.