Not since the premier x-men or the first spiderman movie have I so thoroughly enjoyed a comic book movie. While not a huge fan of Hulk, I was glad that Thor, in the same vein, had great pacing as well as embracing the comic book attitude. The script was engaging and the plot exciting. The pacing kept me interested throughout. Chris Hemsworth nailed this role as he simply oozed the bravado of his character.
I can say without a doubt that while Robert Downey Jr. was perfect for Tony Stark, they could not have picked a better candidate than Hemsworth. As a huge Iron Man fan -- the first, not the second -- I would give them roughly equal ratings, with the edge going to thor as I tend to favor the sword and shield battles over highly advanced technology.
I do want to add a quick note for non-comic fans. Being familiar with The Avengers growing up I had no difficulty following the story. My wife, who was not, said she was slightly confused by the story whether it was following the comic book or the norse myth. She loved the story, the action, all the same parts as me; I just felt I should mention that someone completely unknown to the situation may have questions about the story.
In conclusion, another great work from producer Jon Favreau (Swingers, Iron Man) that will leave you gripping your seat, tense with action-anticipation and pleasantly surprised at the detail of graphics.