Play them in release order. The msx games are good but have 80s Game Bullshit. Mgs1 is a fair starting point, mgs2 doesn't really work as well of your aren't familiar with mgs1 and mgs2 is the smart post modern one that is pretty mind blowing, mgs3 has a simpler plot but has some pretty big emotional moments and the gameplay is something else. After 3, lower your expectations cause it's a mess after. 4 should have never been made, it's a direct sequel to 2 where 3 is a prequel and the ending of mgs2 was intentionally made follow up proof and it shows. Peace Walker and ground zeroes/5 are prequels as well and aren't as bad as 4, I've even got a soft spot for pw, but after mgs3 the series lost most of the sauce.