I'd like to see Emma Frost, Nightcrawler and Rogue done right. (I was completely underwhelmed with the Fox depictions of each character.)
Black Cat (although Sony seems intent on screwing her origins up with the various scrapped projects she has been linked to.)
Hobgoblin (maybe take a page from the 90's cartoon and introduce him before Green Goblin, as Green Goblin has already been tried twice now. It's another one I feel Sony would still manage to screw up, though.)
Dr. Doom (just give him his proper armor, a kingdom and a robot militia. It shouldn't be this hard, as Darth Vader has worked on screen for the past 40 years. THAT'S the template, geez louise!)
Mr. Fear (favorite Daredevil villain, I want the costume too, none of that "evil guy in a business suit" with a skull mask hidden in the background Easter egg bullcrap.)