Ironic that the Marvel film based on the most obscure franchise turns out to be the most successful and satisfying one yet. A real winner of a film, perhaps the perfect example of a "comic-book" movie, helped by winning performances and a canny use of 70s and 80s music that doesn't sound like it would work, but does. Rocket and Groot are of course the breakout characters, but for me Dave Bautista's deadpan Drax stole the film, along with Michael Rooker's space pirate, who comes across as Dennis Hopper after a stint in the Blue Man Group.
Definitely the most enjoyable sci-fi film since The Fifth Element, and perhaps the best space opera since the original Star Wars.