Kind of a counter topic to the disappointing games list. This is for games that really should be a steaming pile of shit, but ended up being amazingly wonderful games. I'm not talking about "so bad it's good," but "WTF this should be shit, but it's actual totally awesome legit!"
As most could probably guess, mine would be:
GO! GO! Birdy Chance.
Hey Tokimeki Memorial is really popular, let's take that idea, dumb it down to the basics, throw in a cheap golf game, and give it an Aim for the Ace/Top vibe. This should be a terrible piece of shovelware, but damn it's still one of my favorites. The game is just really fun and sucked me in completely. It does what it needs to, no more no less and always puts a smile on my face. Having a good grasp of Japanese really helps though as the dialog is a big part of the fun.