Post some under rated games, give them your rating, tell us why we should play it.

I'll start.

Alien Syndrome (Wii (played) and PSP) by Sega

Horrible graphics and story, but the games controls are spot on (Geometry Wars + Dungeon Crawling with leveling and weapons upgrades).  It's actually a lot of fun, and the variety of monsters is pretty cool.  Plus it's cheap.

Halo 3, gears of war and mass effect (360).

Vampire the Maquerade: Bloodlines

Too much bugs, but after u'll patch it with the fans-patch the game will show what's the real RPG is.

Underrated would mean games that didn't receive perfect scores from major publications.

Plus you have to explain why it is under rated.

SSX Blur. IMO it's one of the best Wii games, and it's nailed motion control better than 95% of the other Wii games out there. The game is nothing short of an amazing accomplishment, especially considering how early it came out in the Wii's existence.

Underrated here, of course. :) But if you were talking strictly about reviews (metacritic?, then I have to say Lost odyssey.

It is the best jrpg I have played, ever.

Why would I compare user reviews to user reviews?  I think all three of those games are pretty good, but not under rated myself.  But that is my opinion.

For my next game.

Perfect Dark Zero. 4 player split screen plus smart-difficult bots is crazy fun.

lair

controls are not as bad as people make them out to be. just sit down and play it and in 10 minutes you will be just fine. story was awesome, and the graphics were decent.

I'm assuming this is for the current gen.
If thats the case I'm not sure that I personally have encountered UNDERrated games yet. I'll need to think more on that.