There’s no reason for the movie. The Infinity Stone starts in one place and ends in the same. You can start with the Nova Corps having the Stone and you can skip directly to the plot of movie 2 (because I have no doubt someone will steal the Stone and give it to Thanos because Thanos needs the Stone for Avengers 3).
The movie is just two hours of info for the overall plot for the MCU with explosions between the dialogue. If you already know about the Infinity stuff you can skip the movie.
Ronan was a generic villain with generic reasons to be evil. Nebula was way more interesting, I want to know if she hates Thanos or just goes with the one with more power at the moment. Talking about Thanos, probably the only reason to watch the movie is seeing Josh Brolin as the Mad Titan. He’s amazing.
The Collector was a big disappointment. I thought he would be a villain instead of just… well, a collector. Also, I liked Carina, shame on you James Gunn.
Also a disappointment was the Nova Corps. It felt like they were just there as body count.
It felt like the movie was directed by at least three people. I don’t know, the whole thing was just off. And the dialogue… Gods, it was terrible. Please hire someone else to write the script for the sequel.
One of the few things I liked was the fact that Rocket and Groot were not all the time together and both had their own strengths. The relationship within the main group was the only thing that saved this movie for me (even if they did the whole Gamora/Star-Lord romance, but I’m glad it didn’t stick).
There are waaaaaaaayyyy too many pop culture references. Again, please hire someone new to write the script.