So glad I saved my list from last time this thread was made
1. Electro. Simple, I envy his powers the most. This guy is now on power levels with Magneto, it's been said in the comics itself. But you can see past all of that for a second for two to see such a 3D character. Some stories show him to be a not all that bad villain, other stories are showing him in his prime, kick ass type mood. I think both portrayals can be very effective.
Examples can be his re-birth arc, a prime example of him in kick butt mode providing great "villain" text and classic battles. Heck, he even made Spidey BEG for his life. Then there's Light the Night, where he still has elements of the villain, but other portrayals of beeing scared at times etc.
Then there's his weakness for girls, which is needed really. All villains have a weakness weather physical or mentally, Ock has his ego, Venom has such things as fire. Girls can strike the audience as a usual weakness, for both heros and villains. With Max, they've been used very well. Mia led to his downfall in NA (granted it wasn't glamorous but it showed he really cared for this girl that he didn't just zap her and fly off). Then his wife, who left Max in a bit of a wreck when she left him.
Then there's the costume, oh my yes that costume. As someone mentioned earlier, it's either love or hate, and for me, it's love all the way. The bright colors that just amplify the effect as he explodes onto the screen, it's just sensational.
Best. Villain. Ever.
2. Carnage. Now this guy is plain and simple fun all mixed into one heck of a pshyco. I mean, I can find the character Cletus alone an extemley enjoyable guy. Many think he's just 2D, I'd have to disagree. They don't see through to the reasons he is what he is (abusive father etc).
Aside from that, he's fun. It's fun to watch people beeing horribly masacared and an all powerfull villain justlaughing his butt off while its happening, its fun to see him kick Spider-man around. It's fun to throw up down the toilet after reading "Its a Wonderful life" (I read at a very young age... the the Spider-man corpse sight was what did it).
It's fun to read Carnage.
3. Hobgoblin. Now personally, I think this villain is just so damn cool, it breaks my heart that he hasn't been seen in Spider-man for a long time. What you get with Roderick Kingsley is intelligance, mystery, one cool glider and a very scary villain.
What's best about him? He got away. Right now, he's sitting on a beach drinking tropical fruits and working on his nice tan, and how cool is that? You almost never see the villain get away and I can't help but cheer knowing that this one slick bastard that Spidey couldn't get hold of.