There were high-end WinCE and Symbian devices with large displays and no physical keyboards (or sliders where keyboard doesn't encroach on screen size). To remind, first-gen iPhone was 3.5" @ 320x480 in 2007; for comparison, Dell Axim was 3.7" @ 480x640 in 2005, and by 2007 there were some WinMo handhelds with 480x800.
The thing that really made iPhone different was capacitive touchscreen, and the OS designed around that. WinMo pretty much required the stylus for many things.
Also note “and a first-class web browser” in my compound statement. If you used devices of that era, the browsers sucked at handling most of the web. I knew people who had the previous generation devices (I’m excluding the PalmOS ones I owned since they required a stylus) but nobody used the mobile browser much because it was so unrewarding, and everyone I know replaced them with iPhones due to the web experience.
Opinions varied widely on that - the Flash experience on mobile was horrible enough that it works equally well as an argument that “the web” and Flash were substantially not the same.
It was definitely horrible, but given how pervasive Flash was on the web then, I think a more reasonable takeaway is to say that no mobile device had first-class browser support until HTML5 <video> became prevalent. To me, "first class" implies "I can visit any popular website and expect it to work", which was decidedly not the case for iPhone at introduction.
The thing that really made iPhone different was capacitive touchscreen, and the OS designed around that. WinMo pretty much required the stylus for many things.