How? TDKR is about a terrorist giving a city 'back to the people' and basically taking over it. IM3 is about a conflicted superhero facing his past and personal demons. Not much similarity. Your username has more in common with TDKR than IM3 does.
Back on topic, I liked it. RDJ as usual was the star of the show, but I felt Rhodey in particular improved a lot from last time. Pearce and Kingsley both did great, although I would have preferred that the Mandarin was a more serious villain with more screentime.
~Deadly
To be fair, TDKR also has themes of a conflicted superhero facing his past and personal demons while IM3 has a lot to do with terrorism. So, there are similarities. I wouldn't say they're even close to identical but I can see similar themes.
There was just too much that they did that they shouldn't have done:
-The Mandarin
-Fire breathing Killian
-The Iron Man armors being as fragile as glass
-The "Clean Slate" thing
-The pacing was awful
-The Rose Hill, TN scene was almost completely pointless
-Killian's henchman kidnapping the President
-Extremis
-Tony made several armors for specific world-saving purposes and wasn't prepared for a terrorist attack that he knew was coming
-Getting the shrapnel removed from his chest
-The post-credits scene should have been more like the IM2 post-credits scene hinting at Thor, not a random psych doctor scene with Banner
Overall, I really didn't like the movie.