I'm actually ok with Paul Giamati as Rhino, but this rebooted franchise is going in bad direction. Before you say "Harry is playing Green Goblin not Norman" or "Norman Osborn is supposed to be old and on the verge of death". THAT'S NOT HOW IT GOES IN THE COMICS. Norman was not the verge of death whatsoever. And Norman becomes Goblin first. NOT HARRY. Anyway here is my fan cast. Now keep in mind I can't cast everyone. I'm ranking this as of Top 6 Spider-Man villains.
#6 Jeff Goldblum as Dr. Curt Connors/The Lizard.
Role: Scientist at Oscorp. Known for: The Fly (1986), Jurassic Park (1993) and Independence Day (1996).
Reason: Ifans was terrible in this role. I've heard him for Norman Osborn, but honestly I don't think he would fit that role. After watching The Fly Goldblum would own this role. This role was made for him.
#5 Phillip Seymour Hoffman as Dr. Otto Octavius/Doctor Octopus.
Known for: Punch Drunk Love (2002), Mission Impossible III (2005), and Hunger Games Catching Fire (2013).
Reason: I'm personally not fan of The Hunger Games and Mission Impossible III, but he played a very evil character in those films and he's a great actor. I think he'd be a meaner and more intimidating Doc Ock than Alfred Molina.
#4 John Malkovich as Adrian Tooms/The Vulture.
Known for: In The Line Of Fire (1993), Con Air (1997) and Being John Malkovich (1999).
Reason: Already said.
#3 Aaron Paul as Maxwell Dillon/Electro.
Known for: Breaking Bad (2008 - 2013), Last House On The Left (2009), and Need For Speed (2013).
Reason: AARON PAUL SHOULD'VE BEEN ELECTRO. NOT JAMIE FOX!! After watching Breaking Bad he was born to play this role.
#2 Arnold Volsoo as Quentin Beck/Mysterio.
Known for: Hard Target (1993), The Mummy (1999), and The Mummy Returns (2001 or 2002 not sure?).
Reason: It's an odd idea, but after watching The Mummy I think he'd do a great job.
#1 Gary Sinise as Norman Osborn/The Green Goblin.
Known for: Of Mice and Men (1992), Apollo 13 (1995), and Mission To Mars (2000).
Reason: This was so hard for me to think of because Willem Dafoe was SO PERFECT FOR THE PART,and the only villain I liked in the Raimi series (hell I would cast him again). I've casted both Jason Isaacs and Bryan Cranston, but none are perfect and I always keep changing it. After watching Sinise as the bad guy, he would be perfect for both Norman Osborn and Green Goblin. He play charismatic and play cold calculating evil father to Harry/corrupt bushiness man criminal mastermind personality. He even looks the part.
Now keep in mind this is just my opinion. If you disagree please be respectful.