While I was a bit wary of playing a full blown adventure game on a system with such a small screen and only a touch screen as my input device, I think the porting team did a pretty good job of making the game both pretty and usable for the iPhone.
Graphically speaking, The Last Prophecy looks about as good as I remember it on my PC a few years ago. Both the landscapes of 16th Century France and the interior surroundings found throughout the game are fairly easy on the eyes. Character models are good as well and do a pretty competent job of looking their various parts.
The game's music and voicework also comes through the mobile device's speakers quite well. Of course, for the best quality, you will want to keep your headphones on, and since all of the dialogue is fully voiced, this really is the preferred way to experience the game's story.