Welcome to the club! THIS was the best picture of 2014!
I did a longer review somewhere upthread, but basically it is impressive. The SFX are really well done with a lot of practical effects instead of CGI (the Kyln for example is a physical set), sound story and a slightly twisted sense of humor all set the stage for excellently realized characters both good guys and villains. What's really impressive is James Gunn (Writer/Director) actually gets us to care about these characters. Guardians is his first "big movie" but his previous films (a couple of independent films titled Slither and Super) displayed a lot of the same characteristics.
And, of course, there is that soundtrack! The whole thing is set to a well chosen set of 70s and 80s music that actually is worked into the plot and is part of understanding the character of Peter Quill.
Referring to another thread, watching something like this in comparison to Star Trek Into Darkness makes Star Trek Into Darkness look REALLY bad. This cost less to make, looks better and is so much better a movie it isn't funny.