Ok just got from this bad boy so will give a quick run down on the pro's and con's that I found with this film, that overall has to be said, was a lot of fun.
Pro's
Star-Lord is a great, lovable rogue like character, could have watched a whole movie just based on him, Pratt is perfect as him as well, always liked him since he shot Bin Laden but here this the perfect roll to just cut loose and go for it. Great character.
Rocket - brilliant, Cooper did an awesome job with him too and the banter between SL and Rocket is pitch perfect, very funny.
Groot, Gamora and Drax were all good too, they made a good, balanced if slightly dysfunctional group (which was kind of the point)
Like the quirkyness, vibe and tone of the film, never taking itself too seriously and happy to poke fun at itself at times, Rocket being the obvious example "Oh look were standing in a circle...."
Great costume design and sets, even though you know a lot is green screen it never looks like it.
Cons
The villains, as often the case in Marvel films, were weak. Ronan, Nebula were both forgettable and not greatly fleshed out, just seemed liked dimwits there for the Guardians to rag on.
Thanos, a big letdown, not as epic as he should have been.
The story was pretty basic stuff and pretty similar to Thor 2 in a lot of respects (thankfully a much better film though)
Howard the Duck
Overall though as I first said it was a lot of fun and Star Lord and Rocket make it worth the price of a ticket alone, good team dynamic, a sort of anti-Avengers team but with a similar spark and buzz off each other.
For a score I would say 8/10 seems about fair overall.
In terms of its ranking among other Marvel films, its well up there. Not at the level of The Winter Soldier but pretty comparable to the Avengers and well ahead of Thor2/IM3, but a nice addition to the franchise that has got a solid base to build from now.