Some advice on the PC side of things,
Some care needs to be given to the PC side game servers. Unlike the Consoles, servers for PC games actually have to be monitored regularly and a community has to be created over time for whatever game one is trying to host.
Several of the people who gave care to those servers have graduated and other people must be willing to put the time in to research and be creative for our gaming servers. It simply takes work and effort to host a successful PC game server. This includes learning how to configure the server, finding people to play on it, creating a community within that server, finding reliable internal and external admins to help keep the server interesting. If you are in charge of a server, make sure you are putting time and effort into these things or it is pointless for us to have the server. The best way to populate a server, I've discovered, is to play on other servers, make random friends and tell them, "Hey, I've got this server I'm working on and need to populate it, got any friends that would want to join?" Include admin for those you trust and more than -just you- will be trying to get the server off the ground.
Left 4 Dead needs more than one server (assuming the other one is full often).
The only way to have a successful server is to have at least one person who cares enough to find out what other 'popular' servers do, and imitate it OR do something original that attracts people. Once the server is setup, find people to play on it. As people play they will invite their friends and eventually it'll be full often.
For a LAN there are many games that can be hosted, unfortunately given the -time- allocated to our LANs there is a need for quick paced games which typically come in the form of shooters. The problem with -regular- RTS games is that they typically require a large amount of time to have a successful tournament. This leads to reducing the amount of players available for any PC tournament hosted on top of that RTS tournament (since is is likely the tournament will last a significant amount of time).
Squad based RTS games that aren't based on building a base (such as DOW2 and World in Conflict) lend themselves nicely to tournament play due to their quick pace (for DOW2 there should be concern for the fact that Windows Live could constantly disconnect people on the same network, though not likely).