User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170410043119/@comment-10330822-20170411062107

You are taking this too far. I already stated that this shouldn't be taken as a reflection of the characters contributions, its the relationship to the MC, and no matter how you slice it, they are practically identical. The best friendship/rivalry Issei has with Kiba, the seemingly one-sided rivalry with Saji, the heated rivalry with Sairaorg, and the natural rivalry and conflict with Vali and Cao Cao. They all have their similarities, because when it comes to friendships between men in anime, rivalries like that are very organic, especially when strength is emphasized.

The reason so many people get left in the dust in DB is because not everyone is capable of the same thing a Saiyan is, and even the ones that can, aren't into fighting as much as Goku and Vegeta are. That is why Super has devolved into the Goku and Vegeta show, and they are pretty much dragging characters back into action for the Universal Survival Saga, even ones that have no business being there, like Roshi and Tien.

I'll fully admit DxD has been better about bring the supporting characters along for the ride, and even making them strong in their own right. Its one of the things that make this series so good, you can get hyped for multiple characters. Just look at how much speculation and theorizing is happening for people besides Issei. While in Dragon Ball, its hard to talk about anything without mentioning Goku at some point.