Yeah, you have to write a good story too.
The only people I've ever heard criticise the way The Girl With The Dragon Tattoo is written are writers. It's worth doing as tko suggests and trying to view things as a reader without focusing on technical knowledge getting in the way.
I have friends who read a lot of books and found some of the writing not up to snuff. However, they are prolific readers with a broad knowledge base of books, as opposed to people who jump on the bestseller bandwagon. So they probably have a similar sense of taste to writers than casual readers.
http://vimeo.com/24715531
If you watch that video, I think it explains part of the issue. Merely by being people invested enough in story-telling to become writers, we're not going to be able to function like a casual reader would. Even if you argue the merits of our "taste", it's likely to be somewhat stronger of an opinion than a casual reader has, if nothing else.
This is a forum geared towards writers, not readers, and I think that makes all the difference. Of course most of us read a whole bunch too, but I hope I'm not the only one who sees the mechanics of writing automatically. I can read an excellent book, one I greatly enjoy, and still have a part of my mind pointing out awkward phrasing or sentence structure. And there's nothing a writer likes better than chattering on about writing, their own or others.
For the record, I also hate Twilight because of the general misogyny, rape culture, and insulting weak blandness of the main character. Don't even get me started on 50 Shades.
As Soch, says, this is a forum for writers, not readers. I can read a book that I recognize problems with as a writer, and still enjoy that book. Honestly, it's been a long time since I've read anything without noticing at least a few issues with it, whether it's craft, or story-telling, or world-building, or social issues like rape culture, cultural appropriation, etc. And yet I read plenty of books every year that I enjoy. I read a few hundred short stories a year that I enjoy, too.
There's no such thing as a perfect book. Many books that are published are not that great. They're commercial, obviously. So I don't see the issue with critiquing them. It's not sour grapes, or envy. It's just what people do: they have opinions and they like to discuss them.