During most of my childhood, Dragon Ball Z was a big part of it. I even remember the original Harmony Gold English dub (which was pretty bad in today's anime English dub standards) and of course the original Toonami days of Dragon Ball Z. Dragon Ball Z still holds a lot of weight in Japan even though the series ended in the 1990's over there. Battle of the Gods came out in Japan in 2013 and made its way over here not that long ago. Unlike Dragon Ball GT, this one was written by Akira Toriyama, which I prefer. When other authors write another one's work, it often feels like cheap generic fan-fiction. That's why I hated Dragon Ball GT, and why the rest of the other Dragon Ball Z movies (at the time Toriyama had almost zero free-time to help out) weren't that great except a few of them.
The film takes place before the events of GT (which is probably now considered non-canon for good reason) but a few years after the Buu Saga. With the defeat of Kid Buu, the universe is at peace. However both Old Kai and Supreme Kai learn that the God of Destruction, Lord Beerus has awoken from his slumber by his companion Whis. Lord Beerus tells Whis of a dream he had where he fought a Super Saiyan God. Whis informs him of the all the major things that have happened since he went to sleep, and Beerus recognizes Goku from his dream. Beerus travels to find Goku on King Kai's planet. Goku powers up to Super Saiyan 3 but even his greatest strength is no match for Beerus for now. Beerus wanted a fight with a Super Saiyan God, and Goku apparently is not the Super Saiyan God.
Beerus knows of the other Saiyans on Earth and travels there to question them. Vegeta is given enough warning from King Kai to prepare himself. However even Vegeta knows he will not even remotely win in a battle against Beerus. The Prince of all Saiyans will have to swallow his pride and basically babysit the rest of the Z Fighters and their friends until Beerus decides to leave. The thing about Beerus is that he's the God of Destruction, and while destruction is considered essential in a "new creation", Beerus is rather easily offended. If Beerus even gets a little mad, he'll have more than enough reason to take out of the Earth in the process. Goku realizes he must achieve the Super Saiyan God form in the short time they have until someone offends Beerus.
Overall Dragon Ball Z: Battle of the Gods was pretty good, though it's certainly not the greatest thing to emerge from the series. The animation is amazing, especially as most of the series was drawn decades ago and even Dragon Ball Z Kai doesn't look nearly that good. The ending could have been better, but since Dragon Ball Super came out about two years later, it makes a lot of sense for them to do it like that. Any Dragon Ball Z fans still waiting to see this one really should do so. They already came out with another movie called Dragon Ball Z: Resurrection F which has a return of the villain Frieza which I will probably see sometime in June.