That's not it. In the case of LotR we enjoyed the movies having read the books and knowing exactly what happens. They've made plenty of good Bond films, and it's not like you ever wondered if James Bond would live.
I'll give you that, but I definitely didn't want that to be my main point. The Hobbit movies so far barely have any dramatic hook when compared to LoTR. And I think that can be pointed to a lot of different factors. For example:
-In LoTR we have a great friendship developed between Frodo and Sam. Which is why in each movie most people are moved by that final beat between them in each movie. In FoTR we have Sam running after Frodo when he's on the boat. In TT we have Sam reminding Frodo why it is good to keep on fighting. In RoTK we have him carrying him to the end. Those three beats are already better than anything we have seen in The Hobbit so far.
- Like it has been argued before, the stakes are much higher in LoTR than in The Hobbit so far, at least in this last movie we are going to see the stake of the Hobbit be considerably higher than in the previous two movies with the battle of the 5 armies and what's happening at Dol-Guldur and some characters being presented with the death of those whom they love.
- In The Hobbit, I don't think we end up rooting for the characters as much as we do in LoTR. Thorin comes off as mean and even selfish which makes it hard for us to support this quest, almost as if we had to root for Boromir in LoTR. And I know that is how it is in the book too, but at least in this point of the book I think we are at least rooting for Bilbo, which brings me to my next point. Taking a lot of screen time from Bilbo to tell other stories takes our attention from him. So in this type of scenario I think that's where stretching the movies, though it might be cool at times, it's also hurting our focus on Bilbo. We don't get see him developing as much as we did Aragorn, or Frodo. We do see it, but it's just spread out a bit too much among other stuff.
- Also something we can't avoid is that the awe and wonder of Middle Earth have worn off a bit. In The Hobbit there just isn't that many new things to see. When we watched LoTR everything was new and we were introduced to an incredible world. Coming back to it, though still wonderful, it doesn't quite have that new smell anymore. We'll end up being more critical even about the new things we are shown, such as Smaug, which though I think has been the most badass creature of Jackson's movies, it's overshadowed by all these other little imperfections.
- Sadly The Hobbit with it's rabbit chasing, barrel thumping, half-baked romantic stories, makes it feel more cartoonish and less epic than LoTR
Now all that to say, I do like The Hobbit movies, and have big hopes for this last one. I think Jackson did what he thought was right in his book, which was to show us as much of the story as he could. Bring us to this adventure like many had never experienced it before, through his imagination. I don't know if in the end it would have truly been better to just make one or two movies, we'll get to see some fan cuts at some point, so I guess it's nice we have a lot of footage to play with instead of being limited to make those edits.