You're probably thinking "pahh, how can an iPhone 4S even be compared to a $2500 professional camera", well you'd be quite surprised. Robino Films did a side by side comparison of the iPhone 4S vs. Canon 5D MKII. The rig was made specially for the comparison so you get the same footage in both cameras. They tried to match the iPhone 4S settings as much as possible so it could be as fair as possible.
Obviously the Canon wins due to things like sharpness and depth of field but it is amazing to see a smartphone camera stack up against a pro. With the next generation of Android smartphones coming out in the next few months we may see even better contenders.