There were no good 3G solutions by the time the first iPhone arrived. Existing 3G networks in the US at that time were not capable of supporting enough subscribers.
And I do remember browsing on iPhone compared to other phones. It really was a groundbreaking experience. 3-rd party app infrastructure also appeared quite quickly (in a year) after the phone's launch.
PS: I'm actually still using EDGE on my phone because there's no UMTS/HSPA in my country (there's 4G, but not 3G due to quarrels over radio spectrum licensing). It's fairly OK.