^Stane was a great villain, particularly the way Jeff Bridges played him in the 1st movie. He had an interesting rapport with Tony when they were friends. He clearly had a certain appreciation for Tony's genius even if he was exasperated at having to cover for a bunch of Tony's messes. Then, when we find out he's a bad guy, he's hella scary. I especially love the scene with Pepper in Stane's office. Even though very little is happening in that scene, the tension is quite palpable.
Then, when it comes to the actual fight scene at the end, Stane is still menacing even though, realistically, he probably wouldn't be able to fight very effectively in his armor at that early stage. It helps that, at that point in the movie, Stane has stolen the current chest piece and Tony is stuck with an underpowered Mk. 1 chest piece. It really tilts the odds against Tony, making it that much more impressive when he wins at the end.
Compare that with the "villains" of Iron Man 2.
Hammer is played solely for laughs and shows pretty much zero competance at anything. Vanko is suitably creepy but makes a very poor showing during the fight scenes. He gets in a few good shots during the Monaco fight. But even then, he pretty much gets his ass kicked by the end and hauled off to jail.
Compare this with most superhero films where, in the 1st fight, usually the bad guy totally dominates. Like in the Spider-Man
Sandman & pretty easily escapes their 1st fight. His shapeshifting abilities totally confound Spider-Man at that point.
Dr. Octopus pulls a standard villain tactic of escaping the fight by putting civilians in danger. That way, he can get away while the hero is distracted rescuing the other people.
The Green Goblin pretty much totally dominated his 1st fight with Spider-Man at the World Unity Festival. Only at the very end was Spider-Man able to get any sort of upper hand by blinding the Goblin with a face full of webbing and then pulling out some random wires on his glider. Spider-Man only wins that fight through a couple of very cheap shots.
The point is that, for a villain to be menacing, it helps if he's able to best the hero at least once.