PC Gamer has posted an article (http://www.pcgamer.com/2014/04/25/interview-endless-space-and-stardrive-developers-talk-about-4x-design/) featuring Endless Space's Romain de Waubert de Genlis and StarDrive's Daniel DiCicco chatting about 4x titles: designing them, which ones are their favorites, why they like these types of games, etc. It's a long article, but an interesting read for those who are into the genre.