He was replying to a comment that stated that they didn't enjoy Half-Life but wished they had, and that Black Mesa let them do that. The reply is correct; Black Mesa and Half-Life are different games.

Half-Life is a good game, but it's also overrated because it was so novel for being narrative-driven at the time. It's still a Quake-like arcade shooter at its core, which is great but not new anymore, so people going back and playing the original expecting to be surprised may be disappointed.