Blizzard's Starcraft is the game with the most replay value I've ever played because of the campaign editor. The campaign editor allows you to make your very own missions and link them together to form a campaign. This site is dedicated just for campaigns. The possibilities are endless, just like the stories. Come download a campaign and see what it is all about.
To those of you who have actually made a campaign, please send them to me. I advertise all of them and will post them on my site for you. Send them to [email protected].
The pictures are links to the campaigns, corresponding to the race you control.