Just make it have that arcade touch without the arcade looks & aesthetics (Quake 3 is a major offender here) 

I do have a few specific ideas but also some general thoughts first:

What is important to keep about Quake:

+ Strong atmosphere.

+ Base/medieval/gothic style.

+ Simple visceral gameplay and control feel.

+ Fucked up monsters.

What is not important to keep about Quake:

- Random incoherent feel.

- Lack of story / background sense.

- Crude monster behaviour.

- Specific graphics / themes.

^^^ all of the above also count as "What can be improved in remaking Quake".

I think it would be possibly to retain the feel of Quake whilst upgrading it technologically. Since Quake itself, various games have, in various ways, managed to capture different aspects of Quake enough (e.g. Painkiller, but also bits from Enclave, Q3A, Doom3, and others) to convince me that one could capture the whole of Quake in a more advanced way. Some of what makes Quake Quake IS it's crudity (simple weapons, simple feel, straight-up gameplay), but otherwise a lot of what's special about it is special DESPITE it's crudity, and could be equally special whilst being more sophisticated in both gameplay and looks. More thoughts on that later maybe. 

Yes, I love you. This is the best thread ever. EVER. I'm going to say I don't think Quake should be outright remade; If anyone "remakes" Quake it should just be a true sequel set in the Quake universe, not a remake.

+ Definitely get a strong story going to tie it together. The possibilities are endless.

+The atmosphere would HAVE to be retained in order to keep it Quakey. It's not gonna be all happy and well-lit and still be Quake, is it?

+ Fucked up monsters. One thing I love about the Silent Hill games is how much they remind me of Quake's style, or at least an extension of a direction Quake could go. And Silent Hill has fucked up monsters. Tons of em. I would love to see a Silent Hill influence on the monsters, no doubt. They're scary, creative, wierd, and fun to look at.

+ More awesome weapons. Gimme sumfin' new. The expansions had some "quake realm" weapons, kinda like how HalfLife had Xen weapons. I would love to see more Quake realm weapons. I mean how the Hell is Quake gonna launch this huge inter-dimensional invasion without any weapons, eh? Gimme a Vorehead or something at least.

- / + Base/medieval/gothic. I disagree with Bler on this. One thing I love about Quake is its ability to handle other styles of levels. Don't give me the same things. I'm also kinda tired of Egyptian levels, though I haven't played too many of em. It's just a matter of cliche imo.
I would LIKE to see more metal levels. I thought that was a great style and fit wonderfully in the game. I haven't seen too many of them, but they're wickedly cool. Thumbs up on metal levels and other unique styles.
I still prefer the levels to have the Quakey "catacomb/dungeon" feel though. That's just what Quake has always been, and I see no reason to change it out of the cramped claustrophobic nightmare it was before.

I'm not sure what you mean by " - Specific graphics / themes." You may have to explain that for me.

If some people in the Quake community would ban together... err, I better use a different word in case Scampie reads this...

Ahem. If some people in the Quake community would form a group and start working on a Quake "sequel" I would definitely offer my services. I see absolutely no reason to just "remake" Quake. It should be innovated upon, because there's so much room to be creative AND still retain the feel of the original while tying it all together. Viva le Quake! 

If I had the time and resources, I'd be on this like a fly on shit. 

It should be a open world game like stalker... linear FPS are dead and buried. 

i think monsters would really make or break a quake1 reincarnation.

they must be suitably viscious and devoid of any cybernetics. it's all about the organic beasts.

for maps, i'd say anything goes, really. i'd be all for a painkiller-esque map lineup although perhaps a bit more coherent. a story would be nice, but i'm not sure i'd really demand one as "escape from here with your life" is sufficient for me. 

painkiller-esque map lineup, as in many varied locations, unique texture sets for nearly every map. and not "horde gameplay".

quake gameplay is normally about the viscious encounter between you and a few monsters. although hordes are fun from time to time. ;) 

I can't add a whole lot more in addition to what has been mentioned here but some things to consider are:

- Keep Quake as a codenamed ambiguous evil leaking into the banality of normal earthly existence.

- Either keep the number of weapons down (I find it annoying that some games have way too many weapon types) or limit the number that a player can carry so that you can abandon ones you don't like and pack your favorites. Six or so should suffice. For example, in the original Quake, did you really need the nailgun after you picked up the perf? Expansion packs would add weapons but still keep all the originals. Too cluttered - less would be more.

- Continue having marked secrets that are counted either in level or at an intermission or on a PDA device. Secrets encourage exploration and is a reward for those who want more then just war medals. To be fair, secrets should not be for trick jumpers only (I mean, don't have Painkiller type secrets - keep the Quake tradition here.)

- I like games that have a continous-contiguous world (like Half-Life and most games these days) but to me Quake could still retain it's collection of segregated levels within episodes all linked by slipgates. Quake should make you feel lost, that you are in this multidimensional multiverse, not really sure if you're deep in a planet's core or lurking about the surface of a moon in another universe with no earth. The slipgate concept means that the next level could be light years away from the one you just exited.

- It should have tools and textures and enemies that provide the user community with a lot of creative freedom. If the original Quake was only the 4 episodes and two mission packs, it would have been a good game but would be only a faint memory now if not for it's accessability to both casual and serious mappers and modders. The new Quake has to attract people who like to map and mod or it will be just another play-once and move-on type of game.

- More freaky enemies. Something like those flesh creatures in Hellfire (Diablo expansion pack) or like some of the better enemies in Shrak (Q1 add-on from long ago). The original filty, half-rotted, stinky and blood caked enemies in Q1 felt right.

- I don't mind a more linear flow but not as linear as Half-Life or even worse, the MoHAA series. The original Quake felt about right but some levels could experiment with a more open feel. Perhaps have the odd puzzle level or story advancement level to break up the combat focus.

- Keep lighting important. Consider the geometry of shadows to be of similar importance as the actual surface geometry in this world.

- Find a combat formula that balances fun, fear and strategy. Painkiller was frantic but completely lacked fear or immersion (but could span the spectrum from fun to frustrating). Using either skill levels or some great feat of design, try and produce something that doesn't keep sending players back to a loading screen. Loading screens destroy immersion and atmosphere, lighting and sound cannot provide a sense of escape if the player is either dumped too much or is reloading from saves. I read a good article describing how dying had more purpose in arcade games but with gaming taking on a more immersive quality, alternatives to the die-reload-die-reload paradigm have been succesfully explores (Diablo II and Price of Persia - Sands of Time present two approaches)

- Super graphics are not as important as super design. System Shock 2 did not have great graphics but the game design and story were amazing.

- Make it fun. Make it addictive. Make it a great escape. Keep it simple but sophisticated in the application of design to meet those three things mentioned above. 

I was wondering how the levels should be layed out before the player too. The traditional episode -> levels in linear order seems outdated, but it does present that lost/helpless feeling Quake is good at conveying. You are a pawn of some sort, and following a set path seems like a good way of getting that across.

But then, games like Hexen presented the real-world layout, where you can travel back between levels and whatnot. That also has its merits. It makes the place seem more real. Sometimes you'll activate something which will change a level you've been to already, and the world seems "connected", which is definitely a positive, and can also apply to puzzles/story very nicely. But, this requires a lot of careful planning. A more traditional linear progression could also handle puzzles/story elements, but it would take away from the real-world feel, whereas a real-world feel would add to those elements.

But a continuous world would make level design more of a hastle as well, and mappers that were handling different areas would need to plan their sections together to avoid anything that would destroy the design.

But it's an interesting choice to think of, traditional linear progression linked by episodes or moving Quake in the direction of more modern games: retain the feel or evolve the game.