This question is mostly based on opinion. I mean different people like different FPS games. As well as this, it depends on what the computers can handle, processing wise.
Surprisingly, I found the first Halo game to be of great entertainment when played it in a LAN situation will all my friends. Halo is also great for a small amount of people and a large amount of people, ie. It scales really well... The maps are the right size and the use of vehicles can also entice those non-FPS gamers to join in ;).
It is an old game but heck, if it's fun, why not?
As soragon said, it depends of what you like, what your computer can handle and how much money you wanna spend. If your computer has a good potential the best FPS for me is Call Of Duty (around 50$), otherwise if your computer doesn't have the requirements Counter-strike: source (around 20$) would be a good choice.
For a lan with more than 4 players, Unreal Tournament 3. This is on hell of a good game with friends.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.