The only one that I've ever "owned" is the 5s. Ever since the 6, I started using Jump on Demand from T-Mobile. But from all the ones I've used, here's my ranking:
1. iPhone X: finally the best camera came to a smaller body (had been tired of the Plus models getting the better camera features, like the 6 Plus with OIS and 7 Plus with the dual-camera), and not to mention the all the other changes (design, OLED display, 3GB of RAM on smaller body, etc.)
2. iPhone 6s: the speed difference was so huge, both because of the A9 chip (A8 was very minor compared to the A7), and the 2GB of RAM (which was the first time the iPhone had to wait 3 years to get a RAM increase).
3. iPhone Xs: even though it looked the same as the X, I still really liked the design, and liked that the iPhone finally could reach gigabit speeds.
4. iPhone 13 Pro: really liked Promotion and the big improvement in battery life, but not the heavier weight. Also liked this blue better than the 12 Pro blue.
5. iPhone 12 Pro: ranking this one below the 13 Pro because the 12 Pro Max got the better camera, but I did enjoy the iPhone finally coming in blue (not counting the 5c).
6. iPhone 11 Pro: first time in a long time that I saw a noticeable improvement in battery life, but ranking it below the Xs because of the same design for the 3rd year in a row. Liked the triple-camera system coming to an iPhone for the first time.
7. iPhone 7: ranking this one towards the bottom because I remember that year, we were expecting something different in terms of design (having been used to the "S" cycle, and this phone broke that cycle). Still, the spec improvements were nice, but I disliked it not getting 3GB of RAM like the 7 Plus did.
8. iPhone 5s: even though it was my first phone, Android phones had larger screens by that year. Touch-ID was really nice though, and so was the A7 chip.
9. iPhone 6: the larger screen was nice, but the 1 GB of RAM felt like something that was done on purpose to cut costs, since Apple knew the larger screen would sell itself, and it did. Also, the A8 chip was basically no faster than the A7 chip if you considered the difference in display resolutions between the 5s and 6. And worst of all, the 6 Plus got OIS while the 6 did not (for no good reason).
10. iPhone 8: only ranking this one at the bottom because I only got to use it for 2 months, since the X came very late that year, and this was before T-Mobile started charging down-payments for Jump on Demand, so it made sense to get it anyway.
