There were several things that happened with comic books became serious. Although it started to happen in the 70s, when Denny O'Neil took over wiring Batman, the fact is it really became a big deal with Frank Miller published Batman Returns in the 80s. It was one of the greatest comic book series of all time and it was followed by possibly the greatest of all time: Watchmen.
First, the stories became better. There was no doubt about it. Comics had always been also-rans, not considered real literature or serious, and for kids. Not anymore.
Second, a little bit of the fun that was in comics died. Sure, some of them were still fun and exciting, but really the silliness that made comics of the late 60s and early 70s so much darn fun was lost. Everyone, no matter how silly, had to be ultra-serious. They forgot that what set Marvel's stories, like the Fantastic Four, apart was that it was not so serious and that the team members argued with each other and had fights and stuff.
The same can be said of the best comic book movies. They take themselves seriously, no matter how impossible they are. It makes for an interesting film, but some of the fun is lost.
Thankfully, this is not the case with the new Marvel film Guardians of the Galaxy. Guardians remembers that teams are made of individuals who fight and have problems and creates a team of total smart-asses who make the entire journey fun.
Plot? Ah, heck, this plot is convoluted. Peter Quill, alias Star-Lord, steals an orb that contains something a powerful deity named Thanos wants. Thanos has hired another bad dude named Ronan to get the orb, so when Peter steals it, he runs afoul of Ronan. Ronan has destroyed entire planets, so this is not a guy you want to tick off.
When Star-Lord tries to pawn his ill-gotten gains on the very evolved and populated planet of Xandar, he discovers that others are looking for it. They include a genetically modified raccoon named Rocket and his friend, a talking tree-being called Groot. Also, Ronan has dispatched Thanos' adopted daughter, Gamora, to retrieve the orb. Finally, there is Drax the Destroyer who is out for revenge because Ronan murdered his family.
Somehow they all ended up teamed up and fighting the forces of evil. That's really all you need to know. And the thing is, they have a ball doing it. The dialog is fun and funny, the acting is first rate and the battle sequences are outstanding. It has a little bit of Firefly, that Joss Whedon TV series, but Guardians technically appeared in the comic pages before Firefly so...whatever. The fact is that Guardians of the Galaxy is a ball, doesn't take itself seriously, and is a total thrill ride.
As such, as far as the 2014 superhero movies go, Guardians of the Galaxy ranks right at the top. It has already made a huge amount of money during its opening weekend, so you can bet we will definitely see these characters again.