Apple is very focused when it comes to product lines. They generally don't clutter up a line with variations of questionable relevance. This frees them up to be very on purpose about choices made from iteration to iteration. This is what they're very good at. Now, we can question whether or not these choices are always good ones, but we can't question their focus.
Samsung and other handset makers, on the other hand, saturate the market with phones every quarter. Samsung themselves have nearly a dozen smartphones currently available for the US market alone. HTC, LG, Sony, and Nokia, et al, do the same.
This different approach - throwing every conceivable variation into the ring to see what wins - is quite different from Apple, lacking that focus.