Revolutionary yes, but still overrated.
I will the gave all the credit I feel it deserves: Half-Life had shocking sequences unparalleled in gaming up until that time; frightening and intense battles to death with less than commonplace enemies. It also looked great, sounded great and felt very realistic. It had humor, horror, fairly cool weapons and it was fun to use the security guards as sidekicks.
The multiplayer is a world of its own with what are probably the best mods of all time.
And yet the game is still incredibly overrated. If you look under the surface, the world of Half-Life is really not all that deep or intriguing and as far as gameplay goes it is purely a shooter. For all that is constantly said about how interesting Gordon Freeman is, about how he's not your typical marine running around with a machine gun, I actually find him very uninteresting. He never gets much of a chance to speak during the game and nothing you do can really change the outcome or provoke character development. Although he's a scientist he solves most of his problems with weapons and although some of the weapons allow for some serious creativity, it eventually gets dull.
I will also throw another thought out there: the setting is boring. Black Mesa starts out interesting and then of course it gets trashed, but eventually its a dull place to be trudging around. One thing often said about Half Life is how cool it was to seemlessly go from one area to the next without having to enter different "levels". Perhaps, but when I played it I wanted to go to another level just to get out of Black Mesa. Ultimately there's nothing all that inspiring about your surroundings throughout much of the game. While many people might not care much about this, I think it matters quite a bit for a game that's supposed to be so incredibly great. The military-science complexes of a game like Deus Ex are far more interesting than Half-Life's environments as are the aliens/monsters of System Shock 2 or even old Quake than the bizarre impersonal beasts Half-Life throws at you.
In the end, the game overall is great, but the single-player campaign really disappointed and at times bored me. IMO Half-Life may have been a big leap forward in technical accomplishments, but in terms of storytelling or vastly different gameplay its pretty shallow at second glance.