IMHO, if you want to play Half-Life today, go get Black Mesa, an absolutely fantastic fan-made remake with Valve's blessing:
Unfortunately, by the end of the earth levels and certainly on Xen, the levels switch over to original designs. They become massive and sprawling, boring and confusing. They really should have stuck to doing a like for like reimplementation.
I grew up on Half Life, so playing the first half of Black Mesa a few years ago was one of my favorite adult gaming experiences. But I gave up who knows how close to finish line after Xen was insufferable.
Replacing a 5 minute level with a 20 minute level, even if it's better, ruins that pacing. There's just not enough content in the game to support it.
I agree Xen was by far the weakest of the original levels, but I don't think it's a coincidence that it was also pretty short. I think they knew it had novelty but no staying power and probably cut it to the bone.
> Unfortunately, by the end of the earth levels and certainly on Xen, the levels switch over to original designs
By original designs, do you mean HF1 version, or pre-HF1 designs that didn't get implemented in HF1?
Black Mesa is a masterpiece.
Genuine question, as I own both versions and don't know which to play.