Play MGS 3 first and MGS 4 last.

MGS 3 is really the beginning of the Metal Gear series and since it was released prior to MGS 4, the differences in controls and game play are the least jarring (this refers to MGS 3 Subsistance, which was remastered for the HD Collection, The Legacy Collection, MGS 3D, MGS 3 PSV).

I can't really comment on MGS 5 since Phantom Pain hasn't been released, but unless you can't to wait that long to play MGS 4, may as well play Phantom Pain last.

Portable Ops, Peace Walker, Ground Zeroes all directly follow the aftermath of the events of MGS 3 and build upon events that took place in each previous game, so it makes a fair amount of sense to play those next.

I highly recommend playing MGS 1 before MGS 4 because those are the book ends for the Solid Snake story.

If you're a completist (and since they're included in the Legacy and HD collections), then you'll want to play the original Metal Gear and Metal Gear 2, in all their 8 bit glory, before MGS 1, since those two games are the true beginning of the Solid Snake story. The character is quite different though since those are 80s games.

MGS 2; may as well play that one after MGS 1 and again, before MGS 4.

Whatever you do, you need to play the very first Metal Gear on the NES to completion before you get to even try any other game in the series, otherwise you will not understand anything in any of them!

This is the only real Metal Gear!

I'm watching a playthrough of twin snakes right now and I don't believe there's much difference between this and the original.

It's a remake after all.It might even have more content idk...but I doupt you'll miss anything by skiping the original.

In case you can't get your hands on twin snakes like myself, don't hasitate to watch a playthrough.Cause thanks to the long cutscenes it's like watching a movie.

why?

Apparently the decision has been made already but if not, here's another vote for the order they were originally released in, for the (story-related) reason mentioned. I would advise against playing them in the chronological order until you're familiar with the series, as there's quite a few things you could totally miss if you play them in that order. For example, you might want to be familiar with Raiden before playing MGS3.

The guy  on the cover reminds me of Owen Wilson.

Would you rather watch Star Wars in episode order (I-VI), or in release order? The way the information is revealed is designed with release order in mind. You don't want to know Leia is Luke's sister from the beginning.

Another problem is that you'd play MGS3 first, and that's the pinnacle of the series and one of the best games of all time. The other games might not live up to it after that.

Had you not played any game in the series, I might have suggested you to start with MGS3 because it has the highest chance of hooking you. But if you played MGS4 three times... yeah, I'd say order of release.

It should remind you of Kyle Reese in Terminator actually:

I wonder what was the deal with Kojima basing characters on actors, like Big Boss and Sean Connery.

I love that no one questioned my list. lol