Underrated Games

I Am Alive and Alan Wake (American Nightmare included)

Anachronox and Vangers.

I might be killed for this but i would say Shadow Harvest: Phantom Ops, Space Trader: Merchant Marine.

Shogo

Call of Cthulhu®: Dark Corners of the Earth

Prince of Persia 2008

Bad Rats

The Ship It's really a lot of fun.
Not too fast paced and even somewhat relaxing to play.

Sequence?

grim fandango

The Guild II (The first one was also very good, but the Guild II brings a lot of needed improvements)

I'm not sure right now which may be underrated, but my thoughts on Home, yes it's quite good, my only problem with it is it's advertised as a horror adventure, and when you play it, you find out there's really no horror to it at all. Otherwise, very good game and I hope I can find some of the other endings in it. And if I can think of any underrated games, I'll be back. :)

Game of Thrones (RPG). Character movement is awkward until you get the hang of it, but overall, the storyline was incredible!

http://store.steampowered.com/app/208730/

THE LEGEND of zelda MAjora's mask

The Binding of Isaac

Lone survivor :D

DeathSpank.

Vampire: The Masquerade - Bloodlines -- Still to this day, the closest game I have seen to the original Deus Ex. Awesome game, you have to play it with a community patch to even make it work but it truly is amazing.

Still pretty popular but the S.T.A.L.K.E.R. games should be much more popular than they are, those are also some amazing games. It's still the best atmosphere I have ever seen in a game. I'm a man who loves Bioshock and while Bioshock is known for its atmosphere, I'll take S.T.A.L.K.E.R.'s atmosphere over it.

The Ys games are great for hack and slash RPGs. I personally like Origin a lot more for the better boss battles.