The goblin trilogy is over, so no GG.
I'd like Doc Ock to come back but I don't see how could they possibly motivate him other than amnesia or more of that 'little AI voice in the head' crap, neither of witch will be original or interesting.
What I really want to see back is Sandman.
Now I don’t expect any of you SM3 haters to comprehend this but for any one else who might:
Whatever the departure from the comics is, imagine this - he is the one villain that caused Peter the greatest pain, and Spidey actually forgave him for it. Furthermore he’s still out there on the run. Now if Raimi and co are talented enough to go even further with that controversy, I’d love to see the NY authorities trying to catch Sandman for their own reasons and the only one who can truly do that is Spider-Man…but he won’t. Not only would that finally bring back the edge of ‘NY hates Spidey’ that the movies so foolishly abandoned, but it would also put Spidey in a great dilemma - should he catch Flint Marko, despite the honour he previously displayed towards him, just because NY demands it and he is their servant, or should he try and show the thug’s misunderstood potential to all citizens, risking to permanently damage his own credibility?
Name me one other hero-villain relationship with such a dynamic.
I wouldn’t want Flint to go back to his crime spree or give himself up because that would insult and invalidate the forgiveness ending of SM3. On the other hand I wouldn’t mind the later, if they do it really well, like Sandman victimising himself, just to finally end the whole fuss that was blown far out of proportion. And as the police take him away, he would share a stare with Spidey, which would symbolise something like: “No matter what anyone else might think, at least you and I know the truth.” And then we might have Spidey visit Flint in prison, with at least mildly contemplating on the idea of breaking him out but never actually doing it of course.
However, looking at Raimi’s history of retconning his own movies - he did it with the Evil Dead sequels and he did it with the Spider-Man sequels, despite how SM2 enthusiasts might be blind to this, I’m giving far too much creative credit to him.
So anyways, yeah, the Lizard is the safest way to go.