Which doujin game is your favourite?
I don't know about favourite, but I really liked patchcon, even if reisen made it really unbalanced.
Touhou Pocket Wars(and all the expansions). Even if it doesn't feature my waifu it's a pretty great game.
My favorite is definitely 爆東方幻想郷 Detonate on Sound. The mixture of Bomberman and Touhou worked more nicely than I expected.
Genius of Sappheiros is decent.
Genius of Sappheiros was by far my favorite. I enjoyed that game for well over 100 hours.
Touhou Pocket Wars (Evolution) and Labyrinth of Touhou were also a lot of fun, though the latter got too grindy for my tastes post-game.