Originally Posted by The Overlord
Here is a good question, why is Mandarin Iron Man's arch nemesis? Is there a reason beyond the fact he is the most reoccurring villain from the Silver Age.
I believe that most arch enemies in comics (or in general) usually are some sort of evil doppelganger to the hero/protagonist. I don't think it's as much about what they do
as it is the contrast they represent ideologically, embodying the yin/yang dynamic.
In the same way Luthor represents business & big industry as the antithesis to Superman's good ol' boy American values, or how the Joker's crazed anarchy is a stark contrast to Batman's rigid code of justice, The Mandarin's use of magic in tandem with technology shows a different spin on Stark and how he uses technology & science. Not to mention his appearance (at least originally) of ancient, mystical, Oriental regalia stood in contrast to Stark's modern, American sophistication.
On top of that though, making The Mandarin actually Killian doesn't really make him all that different from Obadiah Stane or Justin Hammer in this movie universe. Just another disgruntled genius trying to get revenge on Tony for some type of perceived slight. I think a more faithful adaptation of The Mandarin would have been more interesting.