I usually hate the femboy anime trope, but Gasper was definitely a great character.

While I dislike fanservice, High School DxD is a really great story that I enjoy

There is definitely a lot of fanservice, but it's one of the charms to it, especially the things that the main character say always make me nearly fall out of my chair.

I also like how it has some Biblical references, such as Mary and st. Michael the arch angel.

Pretty sure that a gooner series

Yes, it sadly is, but if you just deal with it, it's actually really enjoyable and is one of the funniest things I have ever watched.