My son who is 26 years old loves to watch anime. Except for the occasional sci-fi movie, a handful of TV shows (Dexter, Supernatural and Heroes) and wrestling, anime is about all he watches.
Now I don't look at anime because the characters big eyes freak me out. Therefore I don't know much about anime. Some of the anime he likes is
Ghost in a Shell
Bleach
Black Cat
Full Metal Alchemist
Inu Yashu
ChronoCrusade
Dragonball Z
Is it normal for a young man to be looking at anime (rather than porn)?
Anime is the latest annoying pop culture fad. I got out of it a few years ago. It's totally okay, as long as they don't start making statement like "It's not cartoons, it's anime" or "Japanese Shows are better than American ones" and other obnoxious stuff. Make sure he doesn't start using Japanese words in his English sentences.
The moment he starts saying Anime is not a fad, it's a lifestyle, it's time for an intervention.
As long as it doesn't control his life, and Girlfriends remain more important to him than Goku's Power Levels (which are, I believe, quite hight), he's okay.