The reason I liked the original Carnage story arc was that it put a superhero with strict morals (Spidey) against one with warped morals (Venom) and one with no morals (Carnage). Spiderman is what grounded it all. It was an ultimate "enemy of my enemy..." story.
Take Spidey out of the equation and it doesn't feel much more exciting than that final CGI battle at the end of the first Venom.
Couple that with the fact that Venom is more like Brock's wacky roommate and not a menacing force of hatred, and really the only thing I'm interested in is how much Harrelson's going to ham it up.
I still kind of think that the only reason the first Venom was a hit was that it wasn't Spiderman 3. If we hadn't already gotten a taste of just how bad Hollywood can fumble that character, Venom would have tanked hard. It's not a good movie.