I haven't been fannish about the first one (reading fic or such) but was entertained by it, and the second did that as well. I don't regret spending the money on the ticket. I would not watch it a second time in cinema though, but then I rarely do that.

It depends a bit what you want from a Marvel movie, and what characters you are into. It gives more backstory on Quill, Gamora and Nebula's relationship develops, there is team stuff...