Quite a few games made in Japan never leave the shores of their homeland. In some cases it's because the game has explicit content (such as excessive amounts of gore or eroge). Other times it's because the game is from a genre not considered economically viable outside Japan (visual novels, dating sims, etc.). Oddly enough titles which are especially bizarre tend to get exported overseas simply for the novelty factor. Although it is important to note that these kinds of games are not well known even in their country of origin.
Regardless, every once and a while a Japanese game will get lost in the shuffle, slip through the cracks, or simply not receive the recognition it deserves. Just to be clear I'm talking about quality games which for some reason or another have never gone overseas despite having merits worthy of a wider audience. Off the top of my head there are three recent titles which come to mind.
Those are my three picks for this blog post, but there are many more overlooked titles; The grand dad of survival horror Sweet Home for the NES, The modern day JRPG Mother (A.K.A. Earthbound) for the SNES, Shining Force sequels for the Sega Dreamcast, not to mention most of Namco's extensive library of games. All this and more have been denied a wider distribution. It's a little depressing when you think about it, but at least with the help of the internet people can find out about these buried treasures if they're willing to do a little digging around.