iPhone 3G than. Brand new design. It got GPS (which was huge back than). It got 3G support. iPhone 3G's display was better than iPhone first gen's display (better viewing angles, slightly better colours). Significantly improved speakers.I don't consider anything related to camera updates as major. And Retina / IPS is one thing (screen update). So that's just one type of thing (display) - even if you consider the camera updates as major, that's just two types of things.
Never 3.LTE will be in the iPhone 4 first.
Tony
And sure, you could argue that camera updates aren't major. Adding another camera was huge. It now is 'standard' for Apple users, but when Apple added the front facing camera the whole Apple community was like "wow, what, wauw, never! wow, omg!".
And make no mistake, IPS and retina display are different. iPod touch has a retina display, but no IPS. iPhone 4 got two screen updates, not one. You could see this as one upgrade but it really is two.
So for iPhone 4 I now have this as 'major': front facing camera, retina display, and IPS support.
Let's add another one: A4 processor. This was huge as well. Much higher clock speeds. New process line (this is really major). More power-efficient. More RAM.
So: front facing camera, retina display with IPS and A4 processor.