It's been over four years since the first iPhone came out, and a lot has changed, from the screen to the CPU to the form factor. How drastic has this change actually been over the years? Not fast enough.
(Each line of the graph represents a different iPhone spec that applies to every generation. Each mark along the x-axis represents a new iPhone model. Every subsequent increase or decrease doesn't correspond to the raw numbers of each spec, but the factor by which it increased. Every spec in the original iPhone starts as a baseline value, hence the flatline to start.)
It's not like the iPhone hasn't improved. Statistically speaking, the camera, storage and the RAM have experienced the most drastic changes over the five generations of iPhone, with the camera being improved every generation after the iPhone 3G. The CPU has also seen steady improvement after the release of the 3G, though not at the same pace (in comparing the A4 and A5, I used the prevailing logic that a dual-core processor is ~1.6x faster than a single-core CPU of the same speed).
But why doesn't the iPhone have a gig of RAM like the Galaxy S II? Where's the bigger, bezel-less screen? Granted, they've been handcuffed by manufacturers as far as storage capacity goes. But as the biggest and most innovative company on the planet, there's no reason why they shouldn't be trying to not only outgun Samsung, but also themselves.