First two seasons were great, the new season sucks. Gasper is annoying, the plot is boring and there hasn't been much nudity. If there's a fourth season I hope they get back to what made the first two seasons so good. Great ecchi and an interesting story. At least add Irina and the grey haired girl to the harem finally do something worth watching otherwise don't waste my time with a fourth season.
I like this anime, even though the level of nudity was a bit strong for my tastes at times. The characters are all really cool and of course the girls especially It does seem funny to me sometimes that the girls in the real world are not so eager to be that friendly, but oh well I guess it protects them some what from those guys that do all the wrong things. Still shy guys like me don't stand a chance. Okay I don't want to write two much about each one, but I'll do my best Season one of High school DxD was cool. I really liked Rias from the first scene where Issei is introduced to Rias. After that the story developed well and I enjoyed most of the level up Issei stuff in the Occult Research Club. The ending credits to season one was definitely the best, and opening wasn't bad either. One of my favorite parts to this season was when all the action picked up in: Spoiler: Battles When Issei went to save Asia: So emotional to think Asia died for good. And of course the battle with Riser: All the epic's of the characters is revealed. The battle between Issei and Riser at the very end wasn't as good as the team battles I thought though. Season two of High school DxD was just as good. When we start going into the back stories of the characters, it certainly gets all emotional and tingly. Again the opening theme song was good, but the ending credits was poorly done this time. The story flowed well with a fairly decent plot this time, which really brings out some more emotion. The battles also got more intense which was great. Some of the parts I would comment on are: Spoiler I really liked the introduction of Irina and Xenovia those to were pretty cool. Kiba's story was pretty bad ass and emotional. The intro of Serafall Leviathan was really cute, I love her fun personality, I was really unset when Sona said she couldn't stay. And Azazel was awesome he makes everything so funny and cool at the same time. When Gasper arrived I was as disappointed as Issei and Saji. Sir Zechs made a good call at the end with the girls moving in. Season three of High school DxD was "half" good. The story wasn't the best in this one, but it did clear a few things up. The opening theme song was really good, and the ending credits were a bit different this time, but despite that they were still pretty good (better than second season's). I think the ending credit would have been better suited as a opening theme song. Some things to comment on this season were: Spoiler I enjoyed the first half, but after the battle with Loki it started going down hill and by the end I was pretty disappointed (Loki's curse was literally the curse through it). I like the intro of Kuroka, shes pretty good for a cat girl in this anime, if only she acted a bit more cute. Oh and speaking of cute Risers sister Ravel made an appearance, and so cutely warms up to Issei. Issei going juggernaut for the first time was pretty awesome. I didn't think much of all the recap scene's in this seemed a bit early for all those flash backs. Overall the High School DxD series is a good ecchi/ harem anime series. Looking forward to season 4.