3G also got gps and the app store. I'd say that was a pretty significant upgrade.

MacBook Air -> MacBook Air 2: unibody aluminum construction replaced plastic, ssd option introduced.

iPad -> iPad 2: cut thickness and weight by 30 %. A4 -> A5 doubled performance. Dramatically better screen. Introduced the magnetic case ecosystem.

iBook G3 -> G3 dual usb: from colorful clamshell/toilet seat design to sleek laptop. 30 % lighter, half the volume, twice as durable, 2-3x the performance.

And… Apple I -> Apple II? Apple I was a motherboard, the II was a complete computer.