If I take out Peter Parker himself as well as Mary Jane I'm left with these 10:
1. Eddie Brock / Venom
2. Norman Osborn / Green Goblin --- tied with Harry Osborn (the New Goblin)
3. Felicia Hardy / Black Cat
4. Cletus Kasady / Carnage
5. Gwen Stacy
6. Doctor Octopus
7. Doctor Doom
8. Kingpin
9. Electro
10. Hobgoblin
The reason that Venom tops my list is for two main reasons:
1. He is the evil version of Spider-Man
2. He is the comic book re-presentation of Jack the Ripper
Venom