According to Mickey Rourke he and Favreau were all up for making Vanko a more multi dimensional villain but the studio screwed them over:
“[W]hen I did Ivan Vanko in Iron Man, I fought… You know, I explained to Justin Theroux, to the writer, and to [Jon] Favreau, that I wanted to bring some other layers and colors [to the character], not just make this Russian a complete murderous revenging bad guy. And they allowed me to do that. Unfortunately, the [people] at Marvel just wanted a one-dimensional bad guy, so most of the performance ended up the floor.”
“[It’s] ****ing too bad, but it’s their loss. If they want to make mindless comic book movies, then I don’t want to be a part of that. I don’t want to have to care so much and work so hard, and then fight them for intelligent reasoning, and just because they’re calling the shots they… You know, I didn’t work for three months on the accent and all the adjustments and go to Russia just so I could end up on the floor. Because that can make somebody say at the end of the day, oh **** ‘em, I’m just going to mail it in. But I’m not that kind of guy. I’m never going to mail it in.”
“If they let you play the bad guy with other dimensions other than one-dimensional. You have to fight for that though, to bring layers to the character. Otherwise, if you’re working for the wrong studio or let’s say a director that doesn’t have any balls, then they’re just gonna want it to be the evil bad guy. […] So, if you’re working with some good studio guys that got brains and you’re working with a director with a set of nuts that’ll let you incorporate that then it’s fun. Otherwise, you end up with what happened on ‘Iron Man.’”
I agree with him. One of my biggest disappointments after seeing IM2 was Vanko. He really paled in comparison to Stane as the chief bad guy. Hammer was a ton of fun but he was mainly comic relief. The pair of them together didn't come half way close to matching Bridges' greatness as Stane, IMO. But that wasn't their fault.