FYI, I'm a lawyer in my 40s, not some kid, and basically ran out of anything on TV that I could stand, as it was all so formulaic and tired and low-brain. Well, I noticed some anime seemed focused on adults (not the sex stuff, but violence and intelligent plots and stuff), so I tried own -- Sword Art Online. It really opened my eyes to these hidden treasures -- the stories blend fantasy elements with action and interesting characters. Really the main thing I noticed was being surprised by plot twists. Whereas an American TV series or movie you can pretty much guess where it's going to go, this took turns and twists that really impressed me with the intelligence of the show. I mean, Lost took a lot of twists, but they were sort of random/contrived, and my final analysis was the writers were just making it up as they went along to avoid answering any hard questions, very stupid and contrived. Sword Art avoided that.
Anyway, after finishing that anime, I tried several more, and while some were good and still better than traditional American shows, none had the intelligent plotting of Sword Art Online -- till I found Hunter X Hunter, which just totally kicked it up a notch in both fantasy elements, interesting characters, intelligent plot twists you won't see coming, and the like. With some bad guys being sort of serial murderer/pedophiles, it's not for kids, but well done...even those pervy bad guys sometimes redeem themselves, at least for a short time.
How the main characters got more powerful as the series progressed, to be able to best stronger and stronger foes (usually) was well thought out, too, and not overly simplistic. The only downside was that by the fifth (?) story arc involving mutant ant people, I felt it had gotten a bit formulaic and I was not buying into how the world was responding to this threat, and felt the series might have jumped the shark, so to speak. However, I stuck it out and halfway through the arc I really started to enjoy it and the plot kept taking interesting twists. I'm not ashamed to say that I cried at least once because there were such bittersweet moments created.
I don't think I ever enjoyed a movie or TV series more than Hunter X Hunter, and with over 150 episodes, that's a LOT of great TV.