Iron Man is the best superhero origin movie to date (BB and Superman a very, very close second). TDK still remains the crown jewel of the genre. TDKR was sloppy in many ways, but you had to admire its ambition and the general overall quality of filmmaking despite the occasionally weak script. Iron Man 3 is certainly a competent film, and is a respectable outing for the character, but when the dust settles, time will be more favourable to TDKR than it will be to Iron Man 3, and you can take that to the bank.
Here's hoping Man of Steel knocks it out of the park. Superman's origin story is by far the most grandiose and involving out of all the superheroes', and provided it is as good as people are expecting it to be, it may very well take the first Iron Man's spot in the comic book movie hall of fame.