Why do you like Touhou? As in, which is actually the core reason why you love Touhou?
The games. They provide a challenge I can't get out of any other game I have. I've only barely scratched the surface of all the games and they are hard as hell but rewarding when I finally get it figured out. It's kind of difficult to follow the story sometimes because you get destroyed in a stage so many times you fast-forward through the story to get it right. The story in the games has a bit of a relaxed yet serious feel to it and really lets the characters personalities show in how they react to the same situation.
There is a massive world of Touhou fan-made anime, games, and doujin. The one part of the incomplete anime was really good and I hope it gets finished some day. The doujin available and size of the Touhou user-uploads thread speak themselves. For a long time I thought Touhou was an anime, manga, or LN because of all of this content around it. All of the fan-made content shows just how much fans enjoy and support the games.
The visuals in the games are absolutely superb. The bullets and backgrounds are really well made. Most games like this are going for 3D, 1080p, ultra-realistic graphics and this one looks great at 640x480 in 2D. That is really great to see. I wonder how Touhou would do in the western market. I'm guessing get labeled "impossibly hard".