Though the new iPhone is called the iPhone 6, we're actually on the 8th generation of iPhone that has existed. But who cares about that. Let's just see how much the camera—maybe the most important feature on the iPhone after messaging—has improved over those 8 generations. Hint: a lot.
Lisa Bettany compared the new iPhone 6 camera to those of the iPhone 5S, iPhone 5, iPhone 4S, iPhone 4, iPhone 3GS, iPhone 3G and original iPhone by taking the same shot on each. The particular shot above shows the camera's performance when backlit. You can definitely see the difference when you zoom up close.
Here's a portrait comparison:
And a very impressive lowlight:
You can see the comparison in much more detail here. In short: it gets better. Duh. But it's impressive to see by how much. Things might look good from afar on all of them but the cameras of the early iPhones were pathetic shooters. Things that used to be unusable can actually be considered stunning now and what worked in perfect conditions, works even better now.