Venom should return because he didn't get enough screen time in Spiderman 3 even though he's a very popular villain. Norman Osborn was the main villain of the first Spiderman movie and had brief appearances in Spiderman 2 and 3. If Norman Osborn was to be in Spiderman 4, the writers would have to come up with a very good reason why Norman was, all of a sudden, resurrected from the grave.