OK, let's see... to the best of my memory:
iPhone OG - bought at launch and almost immediately sold to a friend, 2G was terrible, no Windows iTunes (I did not have a Mac at the time) and no apps, I remember the pinch/zoom with pictures was cool
3GS - came back to the iPhone once 3G cellular was available
4 - did not like the glass back
4s - still did not like the glass back. At this point I had two AT&T lines with upgrade timelines almost exactly a year apart so I could get the newest iPhone every year
5 - I remember being excited for the aluminum back and LTE speeds, which took FOREVER to actually get in my area
5s - TouchID was awesome
6 - finally a bigger iPhone!
6s SG 128GB
6+ SG 16GB - this is right when I switched from AT&T to Tmo and I had to wait for the 6s/6s+ so this was a temp iPhone, but 16GB was ridic, the iPhone was slow and did not have enough RAM (constant app reloads) exchanged immediately
6+ Silver 64GB - thought the increased memory would help but at this point I decided the 6s+ was the only thing that was going to work for me
6s+ SG 128GB - I remember really wanting the bigger Plus screen size but I just could not handle it (pun intended) quite yet, exchanged almost immediately
6 Gold 16GB - a temporary iPhone for about a week while I was waiting for the 6s
6s SG 128GB - my first Tmo iPhone that I kept
7 Matte Black 128GB- a few month into this iPhone I decided I was finally ready fro the Plus size, and I actually filled up the 128GB so I went bigger...
7+ Jet Black 256GB - my current daily driver, love it!