The original Quake had all the ingredients to make it one oustanding thrill ride
First off, the single player experience of Quake wasn't too shabby either. The best way to describe this experience is with one word: gorefest. The amount of blood and gore in this game is unparalleled. The incredible amount of monsters is outrageous, as they come at you from everywhere and look absolutely horrific. The level design is quite disturbing and looks like your worse nightmare come to life.
The sound in the game was great. The monsters' "howls" were quite frightening. The sound of your guns firing was incredibly satisfying and gave them a sense of true power. The soundtrack was something special, mainly because it was composed by Nine Inch Nails front-man Trent Reznor, giving the game the atmosphere and ambiance it needed.
I already spoke briefly on the weapons in this game, but I'd like to talk about one of those weapons that stood the test of time as being one of the most satisfying ones to fire: the rocket launcher. Anybody who's played Quake will agree that this is the most incredible weapon ever introduced in a shooter. The sheer excitement of firing this weapon and watch it's rockets dismantle the monster or other player (in deathmatch) was heavenly bliss.
Speaking of Deathmatch, with a capital "D", this was the main attraction for this game, namely because it hadn't been done like this before, with such violence and gorish satisfaction and smooth gameplay. I remember playing this mode for hours on end, trying to pick up all the power-ups, from the Circle of Protection, which gives you 666 hit points, to the Ring of Shadows, which makes you invisible (except for the two glowing eyeballs others can spot floating in space) and Quake Power, which was pretty much like Quad-Damage, meaning that your weapons would be much stronger. Oh, and what about mastering Rocket-Jumping? Once you got that down pat, you had a pretty impressive skill to use. Of course, it took some time to get the hang of it, and you had to be pretty patient, but it was worth it in the end. Another side note about Quake's Deathmatch: it was the first one to introduce in-game chatting.
A lot of other shooters have come and gone since Quake (including 3 other Quake games), but none of them can top the sheer adrenaline rush you got from playing this masterpiece when it first came out. That is why it is remembered as being one of the best games of all time.