Quite a weird topic, by virtue of being unpopular, you would think a game could NOT be overrated, as there aren't many people to shout how good it is, therefore not many people to rate it above what it deserved.
Okami is a VERY popular game amongst the "core" gamer group, just because it doesn't sell well, doesn't necessarily represent that it is unpopular, probably a bigger indicator of how much pirating went down at the end of the PS2 lifecycle and what is going down now on the Wii.
I know what you're trying to get at with your topic, but maybe overrated cult following games is a better definition? Okami would fit under that category, seeing as how the Core gamer market is now the minority in gaming. (exaggeration of course).
I'm going to have to go with No More Heroes, seriously, the game is average with attitude, that's all it is and people put it up on the pedestal because it was one of the very few new core games coming from 3rd parties on the Wii at the time.







