Like:
- Pretty much all the characters, both personality and designs
- The music, oh my god the music
- Gensokyo itself and it's mythology
- The gameplay, even though I suck terribly at the games
- The fighters, I suck at them as much as I do at the danmaku ones but at least I can have a few fun matches with friends
- The fan base, yes it has more than its fair share of retards but without it I'd have never have heard of Touhou and it can produce some good stuff at times.
- The colorful fireworks
- Pairings, I'm a yurifag
Meh:
- Memes, some are funny as a joke once in a while but others ("Aya's a slut", Ran's pedo for Chen etc) get annoying quick.
Dislike:
- The UFO system, great idea but it gets me killed way too much ;_;
- Orin's boss battle, she's easily within my top 5 characters but the difficulty of it is too much for me, she rapes me every time and not in a pleasurable way either.
- McRoll, thanks to it I heard U.N Owen Was Her and ended up finding about Touhou in the long run but the fad is annoying.
That's not all of it, but it's a start.