I don't know, I've seen both Highschool DxD seasons and the story isn't that great. Most people watch it for the fan service which it excels in.
Good for you bud.
Storyline is excellent in DxD and it actually has meaning/logic behind some of the stuff that happens. It's all based from Angels, Demons and Fallen Angels. Makes sense, fits to the series, and above all it's entertaining. That's what marks a good storyline. Something that is explained and easy to grasp, yet complex to the series to bring plot twists and emotional moments.
With that said you clearly have a personal quarrel with the series because you're obviously not judging it from the facts, it's your opinions that you're working off of to bring false factors. I rest my case.