Number One online game [to the best of my knowledge], is CounterStrike for Half-Life. [Still available for free download, even though they have made 10 million off of retail sales].

I still play Unreal Tournament regularly every few months, partly because the consistent flow of new in game user mods keeps thing fresh.

In going through in playing all those old games, I downloaded some user made scenarios for Jedi Knight: Dark Forces 2, and some of them [despite a saving problem] are pretty darn good.

My thought: I would not be surprised, if in the next few years, the number one single player game experience ends up being a user-made total conversion and not being a big developer house production.

[Of course maybe could say that have already happened with Half-Life, but I am talking about something you can download for free.]

S