Other than it being the most beautiful to look at and having the most heart, I love the idea that James Gunn had to sit down with Marvel execs and say, "Hey, you know that Star-Lord guy? Yeah, the star of the show. Well, I think he should walk around the whole time with an 80's Walkman playing a 70's mixtape he got from his mom. Yeah, it's a lot like one of those cheesy 70's Gold albums and I want to use it as a soundtrack throughout the entire movie. Yes, even The Piña Colada Song. Oh, and at the end of the movie, Star-Lord challenges Ronan the Accuser to a dance-off to the song Ooh Child by the Five Stairsteps."
If we had heard a synopsis like this at io9 back when Guardians was shooting, I know a lot of people (possibly even myself) would have said these ideas sounded incredibly stupid and would have only worked to compound the already over-the-top ridiculousness of a talking racoon and sentient tree. So, for the producers at Marvel to have the trust and the vision to let Gunn run with this stuff is pretty incredible and because they did it, Guardians stands as the most distinctive film of the MCU and its quirky individuality is one of the things that makes it so remarkable even watching it again. In fact, it is the only Marvel movie I feel like viewing a third time.
I hope Guardians' enormous success means that Marvel will let directors go even further with putting their individual stamps on these characters because it adds so much to the life of them.