I have read a lot of trilogies in my life. And to be honest, I was never exactly sure of what to think about the third and last book. It started with The Hunger Games, then a German triolgy (and a few more of them) and last but not least The Maze Runner. I was slightly unhappy with Mockingjay and I used to say that it feels like it was written by a different author. Divergent is still, in my opinion, better than the last two parts and the same goes for The Maze Runner.
I just recently had a discussion with Julia (btw please blog that one) about modern science fiction and about how it is basically all the same - disaster destroyed the world, new government systems and revolutions et cetera. What I think is why we mostly don't like the last part of trilogies is because we see the bigger picture. Or something happenes that we don't want to happen because shit gets real (sorry). Careful, spoilers comming up ! In the last part of the Maze Runner we find out about the experiment that was done in the maze, in mockinjay Prim dies and there is a war that hurts all the people in Panem and destroys Katniss and in the last part of the divergent trilogy (SPOILER DON'T READ, I SWEAR) when Tris dies, it is not what you wish to read and moreover the whole city turns out to be an experiment too.
I found one trilogy where the last part is the best, in my opinion. And guess what. It's a book where the government tells lies, yes, but it is not that much of a shock. The trilogy is called Die Verratenen (German) and I love it. I might do a book review on that one soon.
Life is not a wishgranting factory. -The Fault in Our Stars
So do we just like books that have good endings? I think yes, because the more you reread a bad third book the better it becomes - you get used to the idea of what is happening and you see from a comletely different perspective. Reading it the first time, you are as surprised/shocked/whatever as the character is... and that is the best thing about reading a book for the first time. No matter how much you wish the plot would take a different direction, you can change anything because it is like in real life: Not a wishgranting factory.