My 2 cents: The most popular seems to be 2G. This annoys me because it doesn't run on a "2G" network. 2nd generation...yes, but that isn't the name of the network. So it seems as though "iPhone Edge" would be more accurate. This is all going by what Apple Marketing says the new one is called though. And IMO, the new one should not be an "iPhone 3G". THEY'RE BOTH IPHONES.
When a new Camry comes out, they don't change the name...it's just a newer model of the Camry. If they build a new interstate for you to drive it on, they don't rename it with the new highway's name on the end. Even if they did (which would be retarded), you're not driving on the same interstate all the time, same as most people aren't on 3G all the time.
Lame marketing has made us decide what to name the old one. So I just call it "the old iphone".