MG1 and 2 are great, but are totally products of their time and total trope-starters as far as the game series goes. MG2 didn't get a goddamned Western Release until almost 20 years after it was released. You basically are stuck with the choice between an Emulator for it or flagging down one of the MGS collection. I honestly prefer the NES version of Metal Gear 1; it runs infinitely smoother than the MSX version and has a number of changes that make it less of a fucking pain in the dick to play.
MGS1 is rough. While it came out in a time when it was
bleeding edge tech on the PS1, the game has a number of structural issues that tamp down just how fun it is, with an insane amount of backtracking and a fucking insane amount of callbacks to MG2 (seriously, almost every single boss-fight in the game is a reference). A lot of quality-of-life improvements the series would get just aren't
in the original, and while it's definitely worth playing, it's aged fucking terribly. If you can nail it, its remake, The Twin Snakes, which was released on Gamecube, is fucking amazing and despite some bizarre gameplay choices is easily the game's most solid version.
MGS2 is the one that everyone loves to shit on, because it sits upon a throne of WTF. The game's plot is ridiculously convoluted, with the game introducing hundreds of new ideas and concepts that only get described in later games, tons of questionable logic, and a narrative that develops attention deficit disorder as you play and can't keep a consistent tone for more than 20 minutes at a stretch. Graphically it was great for the time and it is a decent game on its own merits, but the fact that it basically lied to the fanbase in the promotional materials and the fact that it brought in the character Raiden (who would late redeem himself and become sort of badass) means a lot of people fucking hate it. You can basically skip it without consequence, though it's worth a playthrough if you're willing to give it a chance; this shows a game taking chances that
no developer in the world would have the balls to try today.
MGS3 is widely considered the best one. Though I disagree with this, it is easily one of the best games in the series and fucking
gleams with polish and care. The plot is heavily mired in 1970s-80s politics and uses it quite well as a backdrop for its story, which essentially is the first one, chronologically, in the series. The jungle environments, huge amount of interactivity, and ungodly amount of bonus content make this an absolute treat, and the last half-hour or so of the game is legitimately touching and tragic.
While the most story-heavy of the bunch, MGS4 is notorious for its horrid cutscene-to-gameplay ratio. Fans of the series will want to see how things end, and the game has ten fucktons of great moments, but there's so many issues getting there that it has trouble, and the fact that it's PS3 exclusive and never got an HD release means you actually might have a great deal of bother getting to play it. I like it for mostly trying to do some new things and really trying its level best to provide some level of closure for this confusing spidernest of a series.
Revengeance is a (shockingly) canon story rife with cyborg ninja flip-outs. It's pure bouncy anarchic fun but it also has some interesting callbacks to MGS2 and 4 and gives you a fantastic view into just how irreparably fucked-up Raiden is mentally. The entire game has Autism, but it's one of the hilarious strains and the inability to keep its spaghetti in its pockets is outright endearing. It also has one of the internet's finest memes:
Yes, Hideo Kojima predicted Trump 3 years before the election.
MGS: Peace Walker is a damned solid side-story showing Big Boss' search for meaning following MGS3. It's got some great gameplay, was the first multiplayer MGS that wasn't just a versus game like Substinence's MGO, and the story is the primary lead-in for MGSV (along with ground zeroes). It's available via the MGS Collection, and it's a damned fun game in and of itself, frankly looking fantastic for what is, essentially, a PSP port.
Ground Zeroes is purely setup for MGSV and is essentially a full-price demo for it. While it has a ton of content in and of itself (including a Raiden mission in one version of the game), the game's overall content is pretty threadbare and it exists solely to drum up support for MGSV. All evidence is that Kojima was against making it anything other than a demo so while it's mechanically rock-solid, I can't really recommend you go out and buy it.
MGSV is my favorite one in the series, essentially covering the time between Peace Walker and Metal Gear 1. It is loaded with dangerous amounts of the 1980s and the gameplay is, IMHO, the best of the series. Its story is also, while traditionally MGS-style convoluted nightmare-fuel, filled with some fantastic moments and the open-ended mission design menas you can come up with some.... Well,
unorthodox ways to S-rank a given mission....
MGSV gets a lot of shit because Konami basically kneecapped the game because Kojima kept fucking with them. A lot of story was sliced out at the last minute and while the game still
works ostensibly, it's also got some issues that just aren't resolved by this.
