Not so much in the way of videogame RPG's, but there's two games that come to my mind for being underrated:
- The Disgaea franchise, I enjoy the games quite a lot and some of the humor the series has. Started on the PS2, has a game for the DS, PS3 and I think one or two for the PSP. Personally, I prefer the DS version (it's a game that fits the handheld quite well), but I haven't found myself enjoying it any less on the PS2 or PS3.
- Homefront, and this is a first person shooter. When it was released, the publishing company and the development team (at this time, KAOS) failed to realize how many servers they would need and their servers ended up being overloaded. This caused a lot of network, connection and lag issues with the game early on that turned a lot of people off. (I don't think many of the PS3 community still play this game). As time went on, some glitches in the game (invisibility glitch, for one) cropped up and people left due to this, and due to the small gun selection and so on. I've played it on the 360 with minimal trouble, and I find this game incredibly balanced and just insanely fun. It's such a joy to buy an Apache helicopter and tear up the other team, and it's a joy to go around blowing up campers who are sitting all the way at the back of the map. Plus, the 32 player lobby (for objective gametypes) makes it a lot more chaotic and fun, hard to miss out on the action.
Plus, I don't know who wouldn't love shooting a helicopter out of the sky with an Abrams tank.
Those are the two most obscure, underrated games I've personally played and enjoyed.