Well made B-grade movie who have no backgrounds

Rating: 7/10 (2 August 2014)

Imagine that you are watching the 'Avengers' without watching Thor, Captain America, Ironman, and Hulk. You'll always think "who are they and where they are come from?" while watching movie. The storyline was not enough to introduce themselves.
Marvel should launch this movie after building each hero's background movie like Avengers.
Good to watch. - but it could be kinda B-grade time killing movie if you have no idea of background. :) - bunch of visual effects and slap-sticks that makes you laugh :) - Wordless character Groot, but he's funny enough like Brown(LINE character)
Well made B grade movie, but not an A class.
(At least for me, who has no background of Guardians of the galaxy)