In all honesty its quite forgettable just like the first one, but if you have 2 hours to kill its worth a watch.
Part 2 basiically just picks up where part 1 stwps off, if you really wanted to you could watch them end to end. The storyline is quite predictable and characters very typical of the type of story. The director has obviously tried to use visuals and "epic scenes" trying to make up for the lack of story etc. I feel like this would be far better as a book where characters could be better developed and more depth added to the story.
If you like movies like Riddick, Skylines, or cosmic sin, then this probably for you. I honestly was waiting for Vin Diesel to show up, its typical if his previous sci fi attempts