Except for a couple easter eggs here and there, the two Guardians didn't rely on any other Marvel movie. There's the infinity stone and a couple mentions of Thanos, but that's about it. James Gunn was just able to tell his story without worrying about fucking up the continuity or needing to throw in a scene with Sam Jackson or whoever.

As a fan of comics and one-time fan of Marvel comics, I really like how they're connecting these movies together. I'm not sure that it's ever been done on this scale in Hollywood movies before. But with the exception of Civil War, I think these movies are at their best when they just tell a good, standalone story.