As I type, Guardians of the Galaxy is #41 on IMDB's Top 250 movies of all time. Ahead of … well, ahead of thousands of movies, including The Lives of Others, Sunset Boulevard, and WALL·E. So I don't know about that, but I sure had a good time.
The primary hero is a young Earthman, Peter Quill. In a brief opening scene, we're shown his alien abduction outside the hospital where his mother has just passed away. Years later (roughly present day) he is a full-fledged interstellar Han Solo/Indiana Jones, on the hunt for various valuable trinkets.
But this time he has acquired an honest-to-goodness MacGuffin, a mysterious orb desired by the evil Ronan (who in turn is revealed to be a mere flunky of the even eviller Thanos). Peter is soon on the lam, pursued both by the forces of Ronan, and by the gang of thugs that sent him after the orb in the first place. Along the way, he picks up an odd assortment of allies-by-convenience, who eventually become the titular Guardians: the intelligent-but-deadly raccoon, Rocket; the treelike Groot; green-skinned babe Gamora; brutish convict-with-a-heart-of-gold Drax.
If it were just that, the movie could have been as not-very-interesting as Thor. But someone, I assume writer/director James Gunn, manages to infuse the movie with humor, makes the characters sympathetic and interesting, and fills the screen with inventive visual splendor. Mrs. Salad doesn't like comic book movies very much in general, but gave this her grudging approval.
Consumer note: It's probably worth seeing on the big screen, as we did. We saw it in 2-D, which was fine, but the consensus seems to be that spending the extra money for 3-D, and maybe even IMAX, may be worth it.