The game is amazing.
In a game what would you want more? 'Detail, Gameplay, Story, Interaction with world, what else I am not sure'.
Half Life gave it all. Even the initialization of the game was a Wow. You are in black mesa train, a lady is giving instructions to you through speakers, you watch outside your cabin and you see the big world of black mesa. Engineers, scientists are working through and the view is Spectacular. Then the lady describe what you are and you reach your destination and the story starts.
The game trough out was astonishing. Though the creatures we encounter are creepy but the game won't let you get bored. Personally in the whole game I was very much worried about how do I get out of the black mesa compound but that was a part of excitement.
Release year being 1998, it is still enjoyable for today's people.