War Machine was never an outright villain, but Ironman and WM eventually do get after each other at some point.
The thing I liked the most about Iron Man was the fact that Stark was the focus all the way through. Once the MK III suit was completed, it would have been very easy for Favreau to make the suit the main focus, but by continuing to show RDJ's character, his face, and frequently using his voice, the focus remained on Stark as a character...and not the suit as such. Stark is Iron Man, the suit is just that....a suit.
Thankfully it stayed somewhat loyal to the comics, changing things for modern times...but also stayed clear of the pitfalls most comic book movies venture into (hello Spiderman II and III)
Kudos to Marvel Enterprises for their successful venture into in-house movie production, now let's see if they can rescue the Incredible Hulk from disaster with their 2nd effort.