I massively have to disagree with Black Mesa.
I played it - and it's not even remotely as good as the either of the two Half-Life games. There were just so many backwards design choices that I consider just outright playerhostile, boring or otherwise broken... good god, I still get a headache from it.
The first time I played it, I couldn't stand it and uninstalled it on the same day, installed the original Half-Life and played through that all the way through in one day just to wash out the bad taste Black Mesa left. And the second time, I attempted to use console commands galore to fix what I could - and still gave up halfway through, once again returning to the original Half-Life (followed by the expansions and the sequel plus episodes for good measure) instead.