Atlassian? Oh god. Their software might be ideal for corporate beancounters and expensive consultants, but for everyone else it's a nightmare.
GitLab? A pile of memory leaks and other weirdness.
Google? Not so much, I highly doubt they'll ever re-open Google Code.
edit: and another thing, Github enjoys a massive, massive network effect, next to impossible to recreate by anyone else. Except Sourceforge, but they burned so many bridges that no one sane in his mind will ever trust them again.