Metroid Prime (GameCube)
Perhaps the ultimate hardcore first-person-shooter, Metroid Prime is widely acknowledged for its brilliance, yet has clearly been developed with true gamers as its audience. It requires thought, too - enemies should be scanned with the scan visor to learn their weaknesses and new weapons and items open up new possibilities in previously cleared areas.
The haunting musical score and broken relics from a bygone civilization give the player the feeling that they really are exploring - but with the saddening feeling of being unable to physically touch this strange world because of the Power Suit that heroine Samus wears at all times. Your TV screen is Samus' visor, even frosting up in jets of cold air. The feeling of distance between player and game has never been so perfectly bridged.
With beautiful graphics pushing the GameCube to its absolute limit, massive boss encounters and the kind of solitude formerly reserved exclusively for Lara Croft, Metroid Prime is a gem of a videogame. Looking for something a bit different from the run-of-the-mill WWII shooters and mass-market conquerors like Halo? Give this a try.