IL-2 allows players more than one play option. For me, I like to build and play single, offline missions. I like the overall control that building missions gives me over my gaming experience. While I do a little research to get dates and locations of the battles that occured in the theater for which I am building a mission, I create missions to be an entertaining, fun activity.
Also, I have had to build some missions for practice in flying a certain type of plane, making carrier landings and such.
Early on, I did try out a stock campaign, but found the mission more tedious than fun. So, I abandoned campaigns and stuck with flying my own single missions. I don't think my missions are that complicated for the most part and probably, they are of no interest to anyone else. The only thing that makes them special is that I enjoy flying them and that, I think, is what playing a game is all about.
I applaud the fact that IL-2 also makes it possible to play campaigns, both stock and user created and to play online. To me, the mark of a good game is provide the user with multiple play options and a chance to get involved, e.g. building missions, creating campaigns, etc. Granted, all players may not want to use all play options, as is the case with me.
For me, I have found my preferred way of using the game and that has evolved into playing Dark Blue World exclusively. I am very thankful for Dark Blue World and for the fact that the 'offline option' is being taken seriously.
Cheers,
Riptide