Most new MP games that we will be seeing in the next 3 years will be using the half life 2 Engine. Since Doom 3 has MP support only up to 4 people and Quake 4 will be made off of the Doom 3 engine, Half Life 2 will be the only MP engine left. Most people don't develop their own engines because it's too expensive. The Unreal 2 engine is just about obsolete, and Quake 3 won't be out for a long time, not to mention games being made for it. This means that almost all MP shooters mad in the next 3 years will be based off the HL2 engine. Weather your interested in HL2 or not it’s gonna have a big impact on your gaming life. No matter how good Doom 3’s graphics are, a 4 player TDM/DM multiplayer capability is going to sink it the long term. That kind of MP will stay alive for maybe 6 months.