Hokuto no Ken: Raoh Gaiden Junai-hen

Both are recent remakes of older classic anime. They both focus on a manly protagonist, whose goal is to bring peace and freedom. 

Although their setting and mood are different (with OPM being a comedy and HnK being more tragic), both anime focus on an overpowered main character, who kills enemies almost effortlessly. Both have great art and over the top action. 

Both are action-packed anime, featuring a strong and badass main character. They both have a lot of violence and gory fights. 

The events in both of these OVAs happen in a post-apocalyptic world. The main characters are both tall, muscular and very powerful men. They also try to help innocent people by killing evildoers in gory and violent ways. 

Both are manly anime filled with non-stop action and adrenaline, featuring violent characters and martial arts masters. While they give off a similar vibe, the main difference between them is that G Gundam has mecha in it, while Hokuto no Ken doesn't. 

Post-apocalyptic worlds, deserted wastelands, depraved characters, gore, violence and non-stop action. In both anime, you will find these themes. 

Both films mark the beginning of their set of movies and OVA's. These movies give a tale of men understanding their destiny and the struggles they must overcome.