SourceForge had a messy interface and frankly I hated it. Google Code was like frozen in time, like most Google projects. Microsoft’s thing — I don’t even remember the name — felt half assed and like they were going to abandon it… and they abandoned it. There were also others… none of which I even think were serious enough.
Also Git won because SVN and CVS were centralized VCSes and you needed a server. I can just make Git repos before I even know if a project is serious.
There were other distributed VCSes of course, like Hg, but they either cost $ or wasn’t backed by a major user… like Linux. I admittedly just waited this one out and chose Git because it was more popular.