I've been wanting to make my own movies using PC games for a long time, and am looking for a good game to do it with. I've been trying to get something going with Minecraft, but it has proved more difficult to organize something than I hoped.

If anyone can recommend some good games to make movies with, I'd love to know about them. I already have some ( Medieval Total War 2, Mount & Blade Warband and Sims 3 come to mind.) Whatever I make I'll probably have to do myself, because getting other players to help out has been tough lately. So multiplayer games might not be the best right now.

Depends a little with what you mean with machinima...

WoW is very versatile, and you do not need to actually play the game to make machinimas. WoW model and map viewer extracts assets from the gamefiles and you can arrange them as you like and create scripts.

Halo is used quite a lot, though I have no experience with it.

If you stretch the definitions of machinima, you also use Second Life and Moviestorm, which both are free to use.

I see a lot of people using Source engine games, manipulating actors either through Garry's mod, or Source SDK. You might want to check that out.

Garry's Mod, Source SDK and Source Animator seem the best things to use.