Animes to watch?

Not true.
That was my impression after watching the first episode, but Highschool DxD actually has a really good plot, and a really good cast of characters. Sure it can be pretty heavy on the fanservice, but it's mostly done for comedy and doesn't detract from the plot much.

This is very true.

 Actual spoilers

This is especially true after volume 5 of the novels where character development and plot become a much heavier focus when we're introduced to stuff such as the underworld, ranks of devils in detail, rest of the world(Other gods and stuff such as odin) and more rating games the story never becomes too serious though(Staying primarily on the comedy side of things) and it becomes especially funny when issei summons the boob god and learns how to talk to boobs, literally.