I'm attempting to fill a big hole in my gaming profile by playing all the Metal Gear games. I know how the games flow in terms of MG cannon, but should I play them in that order, or in release order? Suggestions?

Release order. I've only played the MGS games though, but the original Metal Gear games have never seemed too important to play. I was fine just by knowing some of that fiction going through wikipedia pages.
 
I'm sitting here with a copy of Peace Walker that I bought yesterday. Can't wait to get started.

Here's the real question... does one play the MSX version of the original Metal Gear, or the NES version? And does one really need to play them all? I'm speaking specifically about the shitty US sequel (Snake's Revenge was it?) that was summarily dismissed by the creator of the series?

" Here's the real question... does one play the MSX version of the original Metal Gear, or the NES version? And does one really need to play them all? I'm speaking specifically about the shitty US sequel (Snake's Revenge was it?) that was summarily dismissed by the creator of the series? "

Metal Gear 1 
Metal Gear 2
Metal Gear Soild 3
MGS:Port Ops
MGS:Peace Walker
Metal Gear Soild 1
Metal Gear Soild 2
Metal Gear Soild 4

In terms of timeline
 
MGS3, Portable Ops, Peace Walker, MG1, MG2, Metal Gear Solid, MGS2, MGS Rising(when it gets released) MGS4
 
To play them spoiler free just go through MGS1 - 4  in regular order.

playing them in chronological order goes against the point of releasing them how konami and kojima productions have. nobody watches star wars episode 1, 2, and 3 first. same thing.

the original metal gear games aren't really necessary imo. they aren't that great and you're filled in on most of the needed details throughout mgs1. 

" Metal Gear 1  Metal Gear 2 Metal Gear Soild 3 MGS:Port OpsMGS:Peace WalkerMetal Gear Soild 1Metal Gear Soild 2 Metal Gear Soild 4 "

Metal Gear Solid 1, 2, 3, 4.   
(then Portable Ops and Peace Walker, if you have a PSP)

If you can get a hold of the original MSX versions, which were actually included in the Subsistance version of 3 then they're definitely worth playing through if you're up for some retro action.  They're not necessary but they do add a few interesting elements to the stories that are referenced in the later games, quite strongly in Portable Ops especially.  But in general you aren't missing much if you decide to just skip them.  If you're going to, at least do them before the PSP games.
 
I'd also highly recommend you skip the Twin Snakes remake of the first MGS on the Gamecube.  Some people swear by it, but the action scenes are ridiculous.  It feels more like Spider-man than MGS and doesn't fit in with the rest of the games at all.  They also rerecorded all of the dialogue, and while it's higher quality most of it isn't as good.  A lot of the epic lines from the original are delivered with no punch, and generally the voice actors don't seem to have any passion for what they're doing.  Definitely stick with the original version.

Definitely play them in order of release. That way you will be introduced to the characters proper. Going straight for Snake Eater would be stupid cause much of the info you get there will seem weird and unrelated if you have not played previous games released before that even though that is earliest in the timeline. The Metal Gear series story can come off as very complex and might be hard to understand if you do not play them in order of release. I can't stress enough how much better experience you'll have if you play them in order of release. Please, AGAIN, in order of release. :P

i just did played them all this summer and you should play them 1234 and fuck the msx games just read a wiki

In terms of the MGS series, play them in the order of their release.  Obviously that's how they developed them, so they expected people to play them in that order.  So even if MGS3 goes back in the timeline, there are references to characters and events that happened in the two previous games.  I guess it's not incredibly necessary to play them this way, but for me it just makes sense, it's the way Kojima intended it so I dare not argue with him.  Plus you definitely want to play all of them before you get to 4 anyway, because that one ties them all together rather elegantly.  Plus there are a ton of flashback moments that make a lot more sense if you've played the others.  And Kojima has said something along the lines of Peace Walker basically being what he considers as "MGS5."  I don't own a PSP so I haven't played it yet but I'm assuming it'll have all the necessary callbacks to past events and stuff, the fiction of the whole series is just so dense and purposefully convoluted so I'd just recommend playing them in that order to get the most out of it.
 
For the first MGS, you have the option of playing the original PS1 version obviously, but there's also the remake for the Gamecube, Twin Snakes which I thought was better in many ways.  I guess it was mainly the cutscenes that had improved, and you know how important those are to the series.  I don't remember specifically if they made any changes at all to the story, a great deal of time had passed between me playing the original and playing Twin Snakes but I didn't notice anything different.  Annnnd...I could be wrong but I think the NES Metal Gear games that came out over here in America didn't really involve Kojima.  There were two other games that were supposedly better but only came out in Japan on some computer platform.  I think they made these available later on Subsistence or something, but I dunno, I've never played them.  I've played the first Metal Gear for NES and I found it really frustrating and difficult so I didn't get far and don't really know how it ties into the Solid series.

" Annnnd...I could be wrong but I think the NES Metal Gear games that came out over here in America didn't really involve Kojima.  There were two other games that were supposedly better but only came out in Japan on some computer platform.  I think they made these available later on Subsistence or something, but I dunno, I've never played them.  I've played the first Metal Gear for NES and I found it really frustrating and difficult so I didn't get far and don't really know how it ties into the Solid series. "

Thanks everyone. MGS 1, 2, 3, seems to be the way to go, with rounding out the story with the Portable Ops/Peace Walker/Metal Gear games before moving onto 4. Saving the conclusion for last does seem like the way to go.

I think it would suck to jump from good controls  MGS4 and MGS3 and Peace walker... to worse controls MGS 1+2
So yea.. play em in order of realease date

Play them in release date order, you going to have a hard time playing MGS3 if you play it first, is a lot harder than 1 and 2, you better get used to the stealth in the first two games and then go with 3.

Play them in release order.  I will warn you that the controls in the original are pretty damn terrible/frustrating so if you get too frustrated just skip the game and move on to MGS2.  Read a summary of the game if you want to get the references to it in later games.

I would suggest you download the cutscenes from the older games first, then play the newer games... I have Metal Gear Sold (one) and as good as the story/voice acting is, it's a terrible game when you're actually playing it.

MG2 -> MGS1 -> MGS2 -> MGS3 -> PW -> MGS4 
 
If you want, you can cram in MG1 somewhere in that order, just so long as it's before MGS4. I don't really think it's essential, but it's a good game and it depicts the Outer Heaven Incident, which becomes a major part of the storyline.
They're all great games, and even the older ones stand the test of time imo. 
 
I excluded MPO because not only is it not essential, but PW retcons the story so much that it's not even worth considering canon anymore. To see what I mean, read this; 
http://thesnakesoup.org/?section=articles&content=mpwmpo

Metal Gear Solid: The Twin Snakes then Metal Gear Solid 2: Substance. Do not go any further.

No. Not TTS. 
OTT cutscenes, bad voice acting, unbalanced gameplay (ironic, considering that one of the biggest marketing ploys was the ability to play MGS1 with MGS2's gameplay), bad music, and an overall butchered experience. 
 
And it's $30, whereas you can get the original for $10 off PSN.

Well I'm a pro and I play them all the time with my friend Lucas he's a pro too at these games so I'm gonna give you the release order and the chronological order so yeah.

Release Order:

1.Metal Gear (old one for Nintendo NES)

2.Metal Gear 2 Solid Snake(old one too but you can get them and all the games up until PeaceWalker in the Metal Gear Solid Legacy Collection.)

3.Metal Gear Solid 1( for PS1)

4.Metal Gear Solid 2(for PS2)

5.Metal Gear Solid 3(for PS2)

6.Metal Gear Solid 4(for PS3)

7.Metal Gear Solid PeaceWalker

8.Metal Gear Solid Rising Revengeance

9.Metal Gear Solid V(5) Ground Zeroes

10.Metal Gear Solid V(5) Phantom Pain

Chronological Order

1.Metal Gear Solid 3

2.Metal Gear Solid PeaceWalker

3.Metal Gear Solid V Ground Zeroes

4.Metal Gear Solid V Phantom Pain

5.Metal Gear

6.Metal Gear 2

7.Metal Gear Solid

8.Metal Gear Solid 2

9.Metal Geat Solid 4

10.Metal Gear Solid Rising Revengeance

hell of a necro, but this is pretty topical at least.

@swoveman: The MSX versions of Metal Gear 1 and 2 are the real ones, MG1 for the NES is a bad port with a terrible translation and MG2 is a completely different game.

I will never get this question with any series. Every series is meant to be played/watched in release order. The whole reason prequels are appealing is because you have that background knowledge and there's always hints of the future in them that can make them straight up spoiler territory in some cases. So yeah release order.