I think the name is good if you are the only one planning on using it and you're not trying to sell it. It's simple enough to remember to those who visit your gaming server. I hope, for your sake, that Halo2 will allow you to extract the game information so you can make it visible on a website, like some other FPS game servers allow you.
If you plan on using the name as a platform for hosting other servers, then it is troublesom that the name is in its singular form. If this is the case, you may want to register Halo2Servers.com or MyHalo2Server.com.
Either way, it'll have a short shelf life that is pegged to the game itself. Crysis would be a better choice, because it'll be out for the PC before consoles.