I'd say the iPhone 4 is the pinnacle of design. It made all competing smartphones at the time look like cheap plastic toys.
4S, but the tiny screen is antiquated now. I am not a fan of the 5/5C/5S series at all, so skipping them.
Original then the 4s not a fan of any of the others if I'm honest. Especially the 4
This is interesting as the topic is on the aesthetics of the iPhone and not the functionality.
Yet here is an opinion praising the 4S, and not the iP4, when truly they are one in the same, look wise.
Just as it is with people you're attracted to: their personality trumps looks and they either take on an overall more attractive "appearance" or an ugly one based on connection.
Same with the iPhone!
I doubt they would as well. But here is a mock up of one I did. I realize you may not like it but I thought it looked good.
Original then the 4s not a fan of any of the others if I'm honest. Especially the 4
I'm still partial to the original iPhone. I carried one in my pocket for over two years, and that was one of the best-looking and best-feeling phones that I have ever had the pleasure to use. It was also built like a tank!