Competitive

GTR is a "hardcore racing sim" based on the FIA GT racing series. The game does also cater to "average" gamers with arcade and semi-pro modes, but these are not the focus of the game.

Set in the far flung future (the 37th century to be precise), THQ is billing Supreme Commander as the 'next evolution in RTS'. Supreme Commander has widely been referred to as the spiritual successor to Total Annihilation.
The game is focused on using a giant bipedal mech called an Armored Command Unit (or ACU) to build a base, then upgrading units to reach higher technology tiers, and conquering opponents. The player can command one of three nations: the Aeon Illuminate, the Cybran Nation, or the United Earth Federation.

Tribes: Vengeance is the third game in the Tribes series, and the first to have a significant singleplayer mode. It is a sci-fi shooter with diverse character classes, expansive landscapes which can be traveled by foot, jetpack, or vehicle, and bases and base facilities to defend and/or infiltrate. The plot takes place hundreds of years before the previous Tribes games, and shows the events that take place prior to them through the eyes of six different characters over two generations.

Doom II is the second game in the series, and it uses the same engine as the original. It introduced new monsters, a new weapon, and 32 new levels. It is also playable in GZDoom, and most of the information of Doom applies here too.

DOOM needs no introduction. It is the grandfather of the FPS genre as we know it. The GZDoom engine is a port of the originally DOS-based game that allows for high-res OpenGL graphics, mouselook, some widescreen support, among other things. GZDoom - http://grafzahl.drdteam.org/

Hexen: Beyond Heretic is a fantasy themed game, based on the play-style and premise of Doom.

Heretic is a fantasy themed game, based on the play-style and premise of Doom.

Final Doom is a spinoff of Doom 2. It has the same weapons and monsters as Doom 2, but it has 64 fiendishly difficult levels. It is playable in GZDoom, and has the same flaw that Doom 2 does (not pictured)

MotoGP 2 is a motorcycle racing sim from The Climax Group and THQ. It features licensed bikes, tracks, riders, and realistic bike physics and weather conditions. A stunt (arcade-style) mode is available as well.

Wolfenstein: Enemy territory is an online FPS from Splash Damage. Originally created as an expansion pack for Return to Castle Wolfenstein, the project was abandoned in an incomplete state, but the multiplayer component was quite playable, so it was released as a freely downloadable standalone multiplayer game. Gameplay is objective-based and heavily reliant on teamplay.