I just read the first book of the Vampire Diaries, and while there are similarities (i.e. a girl who falls for a vamp) to me it is just another vampire story. I think the major difference is that Twilight is from the point of view of Bella, who is not anything like Elena (though this may change as I've yet to read the next book).
There is also more action in the Vampire Diaries than Twilight overall and it seems darker than Twilight.
I've been reading the blogs and news sites and people seem to want to put these two in the same boat or better yet call the Vampire Diaries the new Twilight.
Here is my humble opinion. The reason that so many people gravitate to Twilight, even though it came out 14 years later than the Vampire Diaries, is that it touches us in a way that the Vampire Diaries does not. At least not yet.
I personally am loving both series, but Twilight just came at the right time whereas Vampire Diaries came before its time.
What do you think? Do you agree, disagree, or have your own thoughts on this?