Iron Man 3
The challenge with an ongoing franchise involving the same character is to give people the character they love, without resorting to just making the same movie over again and again with different villains. This is the challenge that Iron Man 3 faces. The third installment in the Iron Man series (actually the fourth if you include The Avengers) needed to continue the story of Tony Stark/Iron Man without the aid of the rest of The Avengers team. Tricky business.
Director Shane Black could have decided to ramp up the explosions, iron man suits, and creepy bad guys to outgun the past Iron Man flicks, but had he done that he would have lost, because nothing can outdo what Joss Whedon and crew did with Avengers. Wisely, Mr. Black decided to focus on the inner turmoil of being Tony Stark instead of the next big explosion. While there are plenty of explosions and Iron Man suits in the film, there is also quite a bit of actual character work focusing on Tony Stark's ongoing post Avengers anxiety and its effect on his relation with Pepper Potts. The result is a nice mix between quasi-mystery, big action film, character story and techno-thriller.
In the midst of dealing with his personal demons, Tony must confront a new terrorist threat coupled with an old rival from his past. The current bad guys is armed with some new biotech that is a nice departure from Iron Man fighting another version of himself. The villains are weird, creepy, smart and there motivations are moderately believable (with one major plot hole, which my be filled in a later film). If you are a fan of plot twists, you'll be rewarded as well, and the nice thing about this movie is that it leaves room for another sequel, but is a totally self contained film that stands on its own. You won't leave with that, "I wonder how this is going to end" feeling. From this point in the overall Marvel story arc, Iron Man could go a lot of different directions.
Is this the best of the Iron Man movies? No, the first one is still the best, but this is a close second, and worth the price of admission.
Disclaimer, I did not see the film in 3D, as I usually consider it a distraction.