Yes, that's definitely the cause here. The iPhone 4 Picture is much darker, meaning it was made with a higher shutter speed and therefore is much shaper when holding it by hand. If you have a good camera lying around you can try it out by playing with iso/aperture/shutter-speed: Make two pictures in a dark(ish) place, one with low speed and low iso, the other with high speed and high iso (but same aperture). Depending on how dark it actually is and how steady your hands are, you'll see a big difference in sharpness.
The other thing are the colors, which seem much better in Samsung's picture. This, too, has nothing per se to do with the quality of the camera but it's settings. This time it's the white balance that's different. This is one of the things, where camera automatics are still often wrong. A small change of the subject can cause big differences. Moving a few centimeters more to the left is enough...
Again, you can try that with a "real" camera. A DSLR will let you choose the color temperature, but even cheap digital cameras have sometimes different modi for "sunlight"/"cloudy"/"artificial light". I won't go into details here (see [1]), sufficient to say that this can greatly affect a picture.
Also note that the picture from the Galayx II and the one from the iPhone 4S have roughly the same brightness and sharpness. Judging from the noise and resolution, the two cameras seem quite similiar (and are maybe even produced by the same factory).
TL;DR
This comparison is not meaningful at all. For a professional result you would need to control the cameras completely manual and take a lot more pictures in different settings (light, reference colors, tripod, ...).
[1] http://en.wikipedia.org/wiki/Color_balance
EDIT: He actually made more than these three: https://secure.flickr.com/photos/scobleizer