The worst iPhone I've own was the iPhone 3G. Not only was it because of the cheap plastic feel, but also the lack of memory and processor to handle multitasking.
Really? I still love the feel of my old 3G. Actually I grew quite fond of holding it again when my 4S died recently and I had to use the 3G for a while. For a plastic phone, it really feels anything but cheap imo. I won't argue with you about the memory and processor though