This is a cast-list of who I think should star in Spider-Man 4 (Assuming the original cast wont return)
Main Cast (Names in Red indicate that they are original cast members)
Spider-Man/Peter Parker: Milo Ventimiglia (Heroes) - Mainly cause in my opinion he does look the part, and has the ability to bring as much emotion to the character as Tobey Maguire did.
Mary Jane Watson: Hayden Panettiere (Heroes) - She would look perfect for the role if she would dye her hair red, and she would have great on-screen chemistry with my choice of Spider-Man because they have both worked together on Heroes. (Not to mention they are both a real life couple)
Gwen Stacey: Bryce Dallas Howard - She looks the part, but she needs more screen time in the next movie.
J. Jonah Jameson: J.K. Simmons - This guy was born for this role the same way Christopher Reeves was born for Super Man.
May Parker: Rosemary Harris
Probable Villains
(Primary) Dr. Curt Connors/The Lizard: Dylan Baker - He is ...