What about a villain to carry the entire film though? Is there anybody good left after Green Goblin and Doctor Octopus? (While I like Sandman, they had to add way too much to his story in order to try and make him somewhat interesting. If I had my way, he'd be the sort of villain that Spidey would defeat in the first ten minutes.) I would definitely say that although Spider-Man's villains fall short of Batman's, he definitely has some more good ones to use. In no particular order, I'd like to see any of the following:
The Black Cat - If the films want to get away from the Mary Jane romance angle, then this is the love interest that they should go with next. As much as I like Gwen Stacy as a character, they pretty much ruined her in Spider-Man 3, and she's not different enough from Mary Jane for them to go in that direction. Felicia Hardy however, that would be a completely different sort of a story.
She started out as a foe for Spider-Man, but she became one of his allies after a while. What was great about their whole dynamic was the fact that she was totally captivated by Spider-Man but completely underwhelmed by his alter-ego. That could make for some interesting drama, and then you could still toss a villain into the mix.
The Scorpion - What better than another arachnid to take on Spider-Man? Mac Gargan took part in an experimental procedure that gave him superhuman strength and control of a cybernetic tail. Why would he do such a thing? Because J. Jonah Jameson was trying to create somebody to bring down the "criminal" Spider-Man, and Gargan got paid a lot of money for it. The guy not only hates Spider-Man, but he hates Jameson as well. This would be a good excuse to get more scenes with Jameson, which always stole the show in the previous movies.
The Puma - Okay, a lot of comic fans will scoff, but I always kinda dug this guy. He's a super-rich CEO who uses his mystic powers to turn into the beast that you see above. He's a Native American and his tribe had a prophecy that one of their members would one day have to defeat a powerful foe who could potentially destroy the world. Personally, I think it would make for a good story if they ran with that and had Puma believe that Spider-Man was the one he would have to defeat. Since he's not really a villain, he could later be convinced by Spidey's heroism that he has the wrong guy.
The Lizard - This one's a no-brainer considering that Doctor Curt Connors has already been in all three movies. (Okay, he was only mentioned in the first one.) Not only that, but if you pay attention you see that Raimi was sure to give the guy only one arm. Why is that important? Because he's going to create a serum to make him regrow his arm (much as a lizard can regrow a tail) but it will go awry and turn him into the creature you see above. Personally, I'd like to see them go with the intelligent version of him who wants to have reptiles overrun the planet. Considering that he has a wife and kids, the potential for drama is pretty good. I actually think that this guy is the most likely candidate. It'll be nice because he's a villain that Spider-Man has to use his brains to defeat (as he comes up with a serum to turn him back to normal.)
So, plenty of good stuff left over. And after all of them, they can use The Big Wheel.
Ugh. Pardon me while I puke.