Aquaria - PC (completely unheard of but the 'ratings' are very high)
Okami - Wii (rated highly but not many have played it)
Celestial Impact - PC (free open source game that blows away all 'destructible environment' games away)
Warsow - PC (another free open source game that is even more twitch than quake 3)
Einhander - PS1 (maybe not underrated though)
Jedi Power Battles - PS1 (probably my fav star wars game still)
Battleclash - SNES - SuperScope is simply amazing (still have it!)
UN Squadron - SNES - one of my favorite shootem ups
Scarface - Wii - Very fun game with amazing story and side missions that actually affect storyline and gameplay. Coke runs to cuba, building and maintaining a drug empire, and driving around while shooting heads, arms, and legs off of with the wiimote without even slowing down ;)
Killing Floor - PC - was rather unheard of but it recently went commercial and is selling for $20 on Steam so it is doing rather well now. Still amazingly hardcore game, rarity these days.
Way of the Samurai
Way of the Samurai 2
Tenchu - PS1 (both 1 and 2 are superb)
Custom Robo Arena
Shadow of Colossus - PS2 (not played by enough people)
Viewtiful Joe - GC (again not played by enough people)
Swords and Soldiers - wiiware - getting some attention but it is truly a gem and worthy of a full game imo
Phantom Crash - xbox
Geometry Wars: Galaxies - Wii
Metroid Prime 3 - Wii - underrated cause no one ever mentions it when they talk about FPS on Wii even though it is amazing.
ExciteTruck - wii - one of my favorite offline racers of all time next to F-Zero GX and old school mariokarts.
This list could go on for awhie for me but these are the ones I can think of off the top of my head. I know I am forgetting some really important ones but I am at work and can't get too distracted ;)
Current Favorites:
Wii - Muramasa, MH3, Metroid Trilogy, RS2, Okami, RE4, COD, Dead Space, Scarface
PC - L4D, TF2, BFBC2, Killing Floor, Aquaria, Warsow, many UDK indie games
Mods - MechWarrior:Living Legends, Star Wars: Galatic Warfare, PVKII, Goldeneye Source, L4D mods
PS3 - Demon Souls, Way of the Samurai 3
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