Not quite what it was supposed to be
This game has about the greatest 3D graphics you can get without 3D acceleration, on a 486. On modern computers you can set the resolution quite high and enjoy the edgy monsters running smoothly in the atmospheric interiors.
This game also has one of the best soundtracks I've seen in a PC game. I'm not talking about that boring Nince-Inch Nails stuff, I'm talking about the fact that you can play this with any music CD in the drive (my personal favorite for this game is Larry & the Lefthanded's Quantum Rider, but playing Quake with Mike Flowers Pops playing in the background can give you a novel perspective on things!), which is nothing remarkable today, but this was the first game I played that had a CD soundtrack, and didn't need the game CD in the drive in order to run.
While, technically, Quake is far better than Doom, I never could get into it in the same way. The levels are well designed, the monsters are multitudinous, and the guns kill, but the feeling just isn't there. Now if they had opted for a more original approach, as in Duke Nukem 3D, they might have made a classic, but Quake is too obviously just "Doom 3D", and I'd rather play Doom than Quake nowadays.
Oh, yeah, Quake was (and still seems to be) a very popular multiplayer game on the internet. I don't like that. I tried playing over the 'net and these kids who couldn't even spell their names right kept beating the pants off me. I hate death-matches! Put a tax on internet gaming, that's what I always say... and give me my pants back!
The Bottom Line
Play this before you play Doom, if possible. Once you have completed Doom, you have no reason whatsoever to play this on your own. If you like death-matches and you have a dated machine, Quake is as good as the next FP3DSEU, I suppose. Buy Duke3D instead, if you can find it!