I like them in ascending order. The initial outing is the best for reasons already stated here multiple times over. Just a great endeavour. A little lackluster on the final confrontation, but nothing to lessen the experience. It was so great to see that character play out on screen and lead to the MCU (not the Major Crimes Unit
The sequel has it's moments, but is bogged down a bit by Tony being a little too hyper, as well as the Avengers stuff coming across as shoehorned in, though it's remotely connected. God, Sam Rockwell is top shelf.
The third was a bit predictable in the 'hero loses everything, but will conquer and rebuild' facet, but there's nothing there that really dooms the effort. The Mandarin 'twist', however, just outright rankles my Underoos. It took me out of the movie a bit and just had me wanting to get to the end (which boasted it's own predictability in how Killian is ultimately defeated). It really cast a negative light on the entire effort for me.
Great score in this one, the army of suits is beyond awesome and I appreciated that they gave Tony some depth and placed real emphasis on development. **** that twist though. Admittedly, it's petty, but part of the deal in being devoted to and hugely invested in these characters is tossing around a bit of pettiness from time to time. You wanna fight about it?
Iron Man - 9/10
Iron Man 2 - 7.5/10
Iron Man 3 - 5.5/10