I'm confused. Are you referring to HL1? Because of course this wouldn't be highly thought of today. If you didn't play HL1 when it was first released. It is close to impossible to appreciate. Everything in HL1 was copied again & again.
If you are referring to HL2? Then please, hang yourself. Now i love HL1 & HL2 equally, like picking a favorite child to me. However HL2 is the most smooth flowing, well paced, interesting game i have ever played. It flows so well, so much replay, paced perfectly, leaves you stunned at the end & then the episodes. HL2:EP1 was kinda mediocre, but EP2... This was 4 hours of extremely well polished HL2...
A few hours...of a polished....HL2... One of the greatest games of all time...
Now compare this, to some stupid leveled, tit slapping, poo throwing, short, cheesy, Halo-wanna-be, that we have been waiting 15 years for, 2weapon, regen health game that is unmemorable & mediocre.
The thing is, it wasn't that bad compared to most games. But compared to HL2 (as you have)... Cut yourself, do us all i favor.