Project Mammoth

Well, to tell a long story short: I need your help.
A few weeks ago I found a list on Goodreads called Best Books Ever. I voted on it, but since then I`m thinking about it. Why are the books I voted on the best books? Which one deserves the first place and what makes a good book that good?
Here is where your part begins. I thought about the things a good book needs, In my opinion. Now I want to now what your opinion is. What does a good book need? What makes a bad book bad and what are the best books you have ever written?
I started classifying my books, but that eats time, it is a big project, the project mammoth :)
Would you do something like that?
I wish you all a weekend full with good books :)
KJ