We saw Thanos at the end of The Avengers. Thanos is more than a villain, he is a threat to the entire Marvel Universe. "The Mad Titan" is so in love with Death that he wants to destroy all life. He's a true nihlist. He is one of the coolest and most complex characters in comics. He also can not be introduced as an Avengers villain until we see him in space, GOTG is the bridge. Drax (featured in this video) is a long time enemy of Thanos and Nebula (confirmed in this movie) is the grand-daughter of Thanos. Don't forget, he played a pivotal role behind the scenes in The Avengers.

The villain of GOTG has been confirmed to be Ronan the Accuser. This means we will see the alien race known as The Kree. This is probably the beginning of Mar-Vel and Carol Danvers. Carol Danvers is one of the top female characters at Marvel, she is an Avenger and a current fan favorite. I believe we will get her introduction soon.

All I'm saying is that comic book fans can see a bigger picture where the movie fans just can't seen. You don't like the idea of Rocket Raccoon, I understand that but you have to understand that without a machine gun wielding raccoon, we don't get Thanos. Please keep in mind that all of this ties together. This will be a fun movie and hopefully along the lines of Star Wars.