The Twilight Series is popular, but it is not an example of good literature or movie making (and anyone who says it is should be stabbed in the eye with a pencil).
It is very effective at the job of being enjoyable by it's target demographic. IMO good writing is a means to an end, not an end. The author delivered a tale that was captivating to millions of people.

Just because they aren't high art doesn't mean that people should feel the need to lash out at them. If the poor writing detracts you from the story don't read it, but don't feel the need to lash out at the millions of people that are enjoying it. I personally don't care for them at all, but it's not like all of the things I enjoy doing are considered high art either.

Should it be revered as a great literary work? No. Do people really need to heap a whole bunch of hate on it to feel better about themselves? Also no.