“The Vampire Diaries” — the CW’s last best hope for a new fall show to deliver a breakout number — delivered.

“Diaries” (4.8 million viewers, 2.1 preliminary adults 18-49 rating, 3.0 women 18-34) is the CW’s most-watched series premiere ever.

In the adult demo, it’s the CW’s best series debut rating since last fall’s “90210.” Since “90210” scored a very close 4.7 million viewers, the “most-watched ever” claim could change when the nationals come in later today.

As posted last night, “Vampire Diaries” scored high on broadcasters’ latest internal tracking “intent to view” polling among the new fall shows (the most likely breakout programs according to that survey here).

“Vampire Diaries” didn’t seem to much help the premiere of “Supernatural” (3.4 million, 1.4), which was down 18% from last year. NBC’s highly rated presentation the NFL season opener (a very preliminary 17.8 million, 7.5), Tennessee Titans at Pittsburgh Steelers, might have had something to do with that. Still the combo of “Diaries” and “Supernatural” gave the network its best Thursday ever in its target women 18-34 demo.

So NBC won the night. CBS was second with a strong “Big Brother” (7.6 million, 2.6) and repeats. And in third place was — wow — the CW. Fox and ABC were fourth and fifth with repeats.

Vidar – The Norse God of Silence, Stealth and Revenge