Perception and The Superhero movie

My friends told me something today that friends in previous lives have told me - that I don't smile, or smile too little, that I look snobbish (because I don't smile), that I am too sarcastic (worse because I don't have an innocent smile to neutralize the effect), that people think I don't like them. I hate it that it's still true. Over time, I have actually made efforts to smile more, to show more teeth, to look more likable. And now, when my best friends claim they've never seen me laugh and have got used to interpreting my half-smiles as a normal Human Smile Equivalent, I feel a little disappointed.
There are many reasons why I smile sparingly. The main reason, I think, is that I am, through a combination of my upbringing and my essential nature, a rather un-spontaneous person. This bugs me sometimes, because I feel so many things would be easier if I was more impulsive, but I really don't see how I can change that about myself. The lack of spontaneity results in a lack of expressiveness and outward emotion. Though I feel just as much as anyone else, probably more, I express very little. Many years of having held back on expressing myself emotionally have made me forget the language of emotion. I have trouble expressing happiness, sadness, love, affection, anger, sympathy (sympathy is the really hard nut) with the result that I come across as apathetic and unemotional. Which may not be completely untrue.
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On another note, I watched The Incredible Hulk yesterday. It's worth a watch but not a lot more. Superhero movies are fun to watch but almost all look like a patchwork of standard superhero movie elements - the pretty scientist/doctor, the hard nosed military General, the crazy scientist, the experiment gone wrong etc. For that reason too, I love the X-Men movies. They stand out for story, direction and quality of actors in a family of mediocre movies.
That apart, movie franchises are like TV series - they are addictive in spite of lapsing into mediocrity. A James Bond movie or a Spiderman n (though the third was exceptionally bad) is guaranteed to be fun, even if not memorable. The familiarity with characters and the universe and the promise of being shown some solid action translates almost always into a contribution from my side towards the movie's profits.