I love comic book movies on many levels.
At the most "superficial" level (which is not very superficial), they are just great action/adventure movies. They tend to feature strong plot lines, formidable foes, admirable heroes, happy endings, and the possibility of sequel. On this level alone, they are a great reason to go to the movies. But there is more!
Recent comic book movies have taken the lead in pushing new special effects technology forward. They don't just seamlessly integrate computer generated animation into live-action sequence, they also push the boundaries of "Real-D" 3D technology. Best of all, they do so not merely in a mechanical way, but in an artistic way. Every really impressive visual recent movie I can think of is a comic book movie: 300, The Watchmen, Thor, Green Lantern, Sin City, and the list goes on...
But I think my favorite aspect of comic book movies comes from the nature of comic books themselves. At a certain point in the history of comic books - and I'm not sure when, but I'm certain someone more familiar with comic books knows the answer to this - these stories became less about pulp fiction adventure and more about social commentary. The human rights subtexts of the X-Men series has been well-known for a long time.
In general, though, virtually every comic book story is about a normal person who discovers something amazing about themselves, struggles with self-acceptance, and eventually lives up to being the hero they always were. I cannot think of a better message for children and adults than the idea that we all have the abilities inside of us to be uncanny heroes. In some cases, this idea is expressed through dormant physical traits, as in Superman or X-Men; people are born with certain supernatural characteristics that make them different. After overcoming the desire to be normal, the characters are free to express their nature with confidence. (I have noticed that super-villains tend to accept themselves more readily - with certain exceptions of course - but as yet I don't have a good interpretation of this.) In other cases, though, and maybe in the best cases, superheroes start out as ordinary people who become extraordinary through scientific achievement. I like these stories best because they showcase ordinary people doing amazing things without having a latent superpower.
I never feel as inspired as I do after watching comic book movies. I'm not really into comic books per se, but there is no denying that movies with good adventure, rich plots, a good underlying message, and a happy ending are an excellent way to fire up one's own personal ambitions.