It's a small victory I think. Remember that the film was made by Marvel, a fact that was prominent in the marketing. Marvel has become one of those rare studios that can produce a hit based on brand alone. A good comparison (perhaps the only one) is Pixar, which cranked out nearly a dozen completely original hits. The film also suffers a bit from it's contractual obligation to fit into that universe, what with the superfluous references to Thanos and the infinity stones. Plus half the cast is just there to be more important in the sequel, and even some who are important in this film have been slighted for the sake of a sequel.
But, of course, I'm focusing on the negative, which isn't fair, as this is an almost entirely positive thing. The fact of the matter is that GOTG is better than the large majority of summer blockbusters, and has a highly enjoyable tone - the likes of which hasn't been seen in years. Most importantly, except for the Marvel brand recognition, this is a completely alien film property, and it has managed to touch the heart and souls of moviegoers and is now the highest grossing film of the year in the US. If this film convinces studios to take more risks on unestablished live action properties, then the galaxy will be better for it.