I think with this movie, it's going to suffer from Batman REturns/Daredevil syndrome: there IS no central villain, and therefore probably no focus. In fact, there's probably too many villains. Sandman is probably going to be the most foreground villain for the first 3rd of the movie, since he ignites the darkness. Then GG2 for the middle, since Peter clearly unleashes this darkness against him (if the teaser of him with the pumpkin bomb was any indication), and probably Venom for the last 3rd, so Spidey can see the consequences of darkness and will then try to redeem GG2 and Sandy. I'm betting GG2 will go down in a blaze, while Sandman will do the whole "reformed crook" bit and cry a lot in his cell, and Venom....will hopefully die, since I think another movie with him would be redundant. (Side note: I like Venom, a lot. But in cinematic form, there's only so many ways you can tell a story, and Venom basically has just one.)
I'm really hoping this movie will work. I like Spider-Man and how the movies have represented him. But I AM a bit worried.