I dunno. The LG Prada deserved credit for being the first (mainstream?) phone with a capacitive touchscreen, but I think if you're really looking for a spiritual predecessor to the iPhone, so to speak, then -- assuming you don't allow PDAs with phone functionality, like Handspring's line -- the Danger Hiptop, a/k/a T-Mobile Sidekick, is probably much closer. The Prada looks much more like an iPhone but the Hiptop/Sidekick had visual voicemail, one of the best mobile web browsers on the market[1], and an on-device app store. It doesn't get nearly enough credit for the trailblazing it did.

[1] The Hiptop used server-side rewriting of web sites to adapt them to its screen. This seems bananas now, but remember, the web was less than a decade old, and the notion of "responsive design" was years in the future. Back then, most other phones were stuck with WML.