The story hooks you, this isn't your run of the mill ecchi. This is the best ecchi out there, well of this kind anyway.
So first off the bat, you have a character which is almost speaks your most kinky and perverted desires. Issei has no bounds and it really adds to the comedy and the viewer character relationship. Then you have devils, breasts, but not pointless. An example of this is "Highschool Gf The Dead", OK you get it its an ecchi what do you expect but DXD isn't like that, the main character loving boobs uses it to his advantage creating very comical scenes. Then the action is on par with any other anime I have watched, so be it Attack on Titan, Bleach, Sao, Code Geass, DBZ anything... So OK you do get the random fan service, OK I enjoy it, but even if you do not like ecchi there is more to it. If you like ecchi you are in heaven.
You may be thinking, well you may watched some good stuff but your just a kid who watches ecchi and can't appreciate classics like cowboy bebop. Wrong, I have watched it, its good, but There is an experience that I can't get from anything I have watched, so be it deathnote, akame ga kill, aesthetica rogue hero. Highschool dxd got me most hooked and causing me to want a new season.
Seasonwise, 1 is best for me, 2 is good as well but in the lightnovel you don't get the same action anyway. Season 3 was very good, but it could have been so much better.
For viewers who not sure about Highschool DXD I recommend you finish season 1. It's a must, the last couple of ops are worth it.
