As fun and exciting as Guardians of the Galaxy might be, it pulls some punches in terms of arc. Perhaps this is an effect of juggling too many characters, conference-room screenwriting, or the editing room floor. Whatever the reason, we have:
A main character that changes from being concerned about reputation and money to being concerned about a girl (not a big stretch) to self-sacrifice, without much to inform the arc along the way. The self-sacrifice is weak, too. Without giving away spoilers—he was about to die anyway.
Groot has a heart from the beginning and still has a heart at the end. He's a lovable character, but he doesn't change.
Gamora shows vulnerability and desire to be free that informs her goals quite well, but even though she struggles to save her enemy in a critical moment, she is much the same at the end as she was—just free from her father now.
Rocket the raccoon eventually gives in and does something warm and fuzzy, though I couldn't say exactly what events led to that change. Drax admits to having friends and sets his revenge goal on a lesser tier, and I think Rocket's arc is much like this. He isn't choosing self-sacrifice as much as he is choosing to stay with his friends. Still, in the cases of both Drax and Rocket, the arcs felt a little thin and underdeveloped to me, though still present.
But what do we want from a movie like this? It's meant to be fun, right?
Hell yes it is fun. And maybe some stories can be merely fun with no heart to them, but Guardians doesn't fall into this category because of the simple reason that it tries to have heart, but really doesn't. It sets things up. Rocket doesn’t feel accepted; Gamora only wants to be free of her father; Drax doesn't need anyone's help, he only needs revenge; etc. All of these things set my expectations, which left me feeling unsatisfied by the end despite the excitement.
Perhaps it all just sets up the expected sequels.
Writer of speculative fiction. Current work in progress is an untitled dark fantasy novella.