Starting on the protagonist, (by far my favorite) Issei Hyoudou has a lot he brings to the table. If you are a fan of crude humor and sexual jokes, you are going to love this. The main quality that makes him an enjoyable character is his pervertedness. Issei has NO mental filter that keeps him from saying embarrassing things. This is a large part of the comedy in High School DxD. Scott Freeman does an excellent job portraying Issei Hyoudou. DxD got the nomination for the best male and female voice performance, with Scott Freeman playing Issei and Jamie Marchi as Rias Grimory. The show received the BTVA Anime Dub Television/OVA Voice Acting Award in 2015. Along with being a complete pervert, Issei is also reliable. This is his heroic trait that allows him to save the day and appeal to the ladies (despite his unpopularity).
The story continues to keep the flow with new and exciting elements as well as hilarious comedy. The process of the protagonist going from a loser to a hero is comedic as well as exciting. There are little to no let downs in the story (depending on how you look at it). Even non-ecchi fans can love this show.
The art is one of the best a harem show can deliver and due to its overwhelming popularity, there is speculation for a 4th season.
Even if you aren't a fan of the ecchi genre, I recommend giving the story and comedy a shot before disregarding it all together.
