Having worked with all three, nothing but Stockholm syndrome would keep anyone to switch from cvs. Likevise the switch to git for open source happend (In my opinion) in large part because Github offers a far better experience than SourceForge witch was dominant at the time.
There was actually a brief period where Google Code was ascendant, but then GitHub was demonstrably investing more in collaboration.
I think one aspect of Git that is really important is forking, and having your own local commits. Merging commits and patches in svn were awful. You wouldn't ever allow someone random to join your svn repo, but if they can reasonably provide a patch, you could take it. Git makes that massively easier.
