Both Yesterday & Today:

Green Goblin

Green Goblin for me - although if he'd stayed dead after dying (as in: no Harry Goblin, no Hobgoblin), I think Dr. Octopus would have taken the spot.  But that's like asking water not to be wet.

Monday 12/15 toss-up: Magneto - poorly named or expansively-abled?

Catching up:

The Green Goblin killed Gwen Stacy in one of best-written comic I've ever read. Man, that's still a powerful scene, even though I've seen it a million times. But no matter what, the Goblin knocked Gwen off the bridge and the fault is his alone.

Spider-Man's arch-villain is the Green Goblin. No doubt about it. However, Spidey has such a great cast of villains. I'd rank his rogue's gallery second only to Batman's in all of comics - and it's a close second at that. If the Green Goblin had never been created, Doctor Octopus would be a fine arch-foe.

Magneto: Great villain. Lousy name.