If you loved DOOM or DOOM II then Quake is a god-send. The Original Quake was THE FIRST TRUE 3D First Person Shooter ever made. And it did (then as well as now, if anyone could see past then next CoD) phenominally.
32 is the magic number when it comes to great FPS' , as all 32 levels (and 6 underplayed 'Deathmatch' levels) were intense and enjoyable from start to finish.
The Original Quake may as well have been a DOOM spin-off during it's initial release, but copying a great formula isn't always a bad thing, IF you know where to go with it. Quake knew EXACTLY what it was doing, and IMPROVED upon all of DOOM's previous work. Taking DOOM 2's 32 level formula, the ability to look up and down (It was REVOLUTIONARY I TELL YOU!!!!!!!), intense gore (which, back then made the game "M for Mature" but now, with graphical updates, the gore has been downgraded too "T for Teen"), fast-paced (CoD has NOTHING on this) multiplayer, and over the top violence (A.K.A. The AXE OF EXPLOSIONS, seriously... no joke... go smash up a corpse with this thing...), that made it a 'Must have' for EVERY gamer that owned Windows 95.
NOTICE (FOR CLARIFICATION ONLY, You can skip this if you want):Now, I must clarify one thing, I didn't grow up on DOOM or DOOM II or even Quake, BUT I believe Wolfenstein, Spear of Destiny, DOOM, DOOM II, Quake, and all of the other great 90's First Person Shooters are what we should all take a page from when making the next CoD. SERIOUSLY my first First Person Shooter was CALL OF DUTY 4 for God's sake! When I played DOOM for the first time I was... how shall I say this....MIND BLOWN, FLOORED, & BLOWN THROUGH THE FRONT DOOR! SERIOUSLY! I play CoD 4 now and I'll ALWAYS go back to DOOM & DOOM II before the day's up.
The Original Quake is, in my opinion, better than Quake 2 & 4 (Which are basically part of a 'mini-trilogy' I call
"The Quake Wars"), Quake 1 is entirely seperate from the rest of the series. It is closer to a fully 3D DOOM game more than Quake's 2, 4, and Enemy Territory: Quake Wars (A.K.A The Quake Wars Trilogy) Quake is the name of the final Boss in this game, though (Can this really be a spoiler? I mean, all I said was the name, right?) not a boss in The Quake Wars Trilogy, has no mention of even the name "Quake" EXCEPT when the Intro of Enemy Territory: QW has a slip-gate (pretty much a space teleporter) shaped like the logo summon invading ships.
NOW, all mentions of other games aside.... Quake is an addicting, fast paced, rocket jumping (yes, we has those), barrel O' fun. In the words of a wiseman ~ "In my day, we rocket jumped to school, both ways." - Wise guy, 20XX (because I don't remember his name or the year). You would be a FOOL to pass this game up, give it a try, there's NOTHING to lose, and everything to GAIN!
P.S. It is ALMOST REQUIRED to have this installed onto the game to make run properly on modern PC's: http://forums.steampowered.com/forums/showthread.php?t=1756923
(The ULTIMATE Quake Patch IS LITTERALLY the 'Best Thing Since Rocket Jumps')