The near-complete lack of shmup-related posts on Danbooru vs the 4,000+ shmup-related posts on Pixiv really shows how much more popular the genre is in Japan than in the West.

Here, thunder_force has only 2 posts.
But on Pixiv, a search for サンダーフォース (sanda- fo-su -> Thunder Force) returns 225 results (although admittedly a plurality of these posts wouldn't get approved here for quality reasons). I even managed to find an R-18-rated image of TFV's main character.

Not to bring up too old a post... but yeah.

I find this with a lot of series; Danbooru's userbase just seems to ignore a lot of good art because they're not looking for it.