alot of you guys are saying that it needs to be dark...but peter doesn't know whats going to happen...he knows that right now everything is perfect for him, but he knows that nothing stays good for long, and he will exspect something to happen, but you can't really have the voice over having him saying dark things because at that point he's not.
the voice over in spidey 1 at the begining was telling the story. once you got to the end of the movie the voice over caught up with him and now we were going to see the story as he lived it in spidey 2...so naturally we are seeing the story as he lives it again in spidey 3 since no voice over at the end in spidey 2. so he can't know he turns bad if he hasn't lived it yet.