I do not think anything could replace all the memories I had has a kid playing the first half life.
Black Mesa it self is a wonderful recreation of the original that puts into play the current technology of our time. Better graphics, lighting, sound. The things that made the game what it is today are still there. The useless security guards, the scientists that seem to have never done a push up in their life, the cheese one liners, the over confident army, all of this still rings true to what Half Life is.
It is meant to be a game that allows you to enjoy the story and still get your brain working. Its not overly difficult to beat yet you feel you didn’t waste your time.
So no in my mind the original HL can never be replaced.
Edit: I actually felt that some of the changes to shorten a few areas where greatly needed. I went back and played the first HL before playing and beating Black Mesa and I found my self really enjoying the changes, it made it have a better flow, rather then doing a puzzle that added a extra hour to the game that really, in the long run, wasn’t needed.