The Importance of a Thrilling Plot

I have been reading extensively during the past few weeks - wonderfully great and truly horrible books, I'm disappointed to say.

So what is it that makes a novel great?
How important are the twists and turns of the plot?

Of course, the answer isn't simple.

I'll take a few examples.

I have recently read the paranormal romance novel Hush, Hush by Becca Fitzpatrick.
The first thing that struck me about it was simply that while there were no obvious grammar errors, it suffered from other major problems that had me wondering if I should laugh or cry (so most of the time I chose to just roll my eyes and swear a lot). One of these problems was character development, where we see teachers behaving as if they're middle-grade bullies, a best friend who's so stupid and simply evil towards her supposed best friend that we wonder why the MC sticks with her, and the always-so-lovable damsel-in-distress, I-should-go-into-a-dark-alley-by-myself MC, who makes the reader want to rip one's hair out of one's scalp.

Yeah. I'm not being nice. I'm trying to make a point.

So why did I read it in one day and craved for the sequel?
For the simple reason that it had a very hooking plot. I just had to know what happened next.

I have also recently read Fallen (in the same category) by Lauren Kate.
The idea was one I worked with for a while last year, without my knowing that it already existed in some form, so the idea had every opportunity to deliver - but it never did.
It had all the same problems as Hush, Hush, with the addition of never feeling like you 'lived' it at all - you were a spectator watching it happen from above. No characters intruiged me; not even the boy she's supposed to love, and that seldom happens. And we got all these mysterious clues, which were the only ones that kept me reading, and then - for some reason - the author decided that no, we were not going to learn about these things until in later novels. Major downer. The plot wasn't even exciting.
So no. I refused to read any of those sequels. Her novel gave me a headache.

The only clear difference between the two is the plot.
Which leads me to the conclusion that plot is more important than anything - even more so than character development (sometimes). Hmm. I'm not sure I agree with myself here.
Ah, well.
Plot is important, let's leave it at that (but we all knew that already, so what was the point...)

Now I'm off to write a plot twist!
(No, I'm actually not kidding!)