Both feature a main character with a special power and group of friends traveling together
Both feature knights and magic
Both have dragons
Both have a main character that can connect to a special being that most others can't connect to
Both are fantasy and involve adventuring
Both are based off games
Both series are adapted from games. Generally both tackle about a group of travelers, that started in a few numbers and later on joined by some valuable allies, as their travels encounter more adventures. Although, Granblue is lighter by nature and plot compared to Ragnarok which is darker and tragic at some points.
All aboard the feels boat, because this is going to be the greatest journey of your life. Wanna travel across islands and discover what lies at the very end of the world? Then this is your last chance, last opportunity. But don't fasten your seat belt yet because you need to draw your weapon quite often, actually.
Boy and his cute familiar meets a cute girl in distress chased by evil empire.
Boy decides to help her for no other reasons that she is cute.
They both go onto an adventure while still being chased by an evil empire.
Both are shounen in fantasy settings made by A-1 Pictures.