Everything before Xen I'd say is either better or at least as good as the original Half-Life, but Xen really took the wind out of my sails. It looks gorgeous, but overall its just a slog. I liked the Xen chapter at first but it very quickly wore out its welcome and sadly the game never recovered. Gonarch's Lair made a bad boss fight just a mediocre one that took forever and Interloper is a warcrime, but Nihilanth is alright at least. This really solidified my opinion that Half-Life is mostly really good, but missions like Residue Processing and of course all of Xen are really rough. The game peaks at Surface Tension and doesn't recover. Sadly, Black Mesa just made that feel even worse by making the 90ish minute Xen of the original this four hour monstrosity.