From best to worst I'd say -
Metal Gear Solid - Classic
Metal Gear Solid 3 - Classic
Metal Gear Solid 2 - Great, although I'm still mad about having to play as Raiden
Metal Gear Solid 4 - Good, but they went a little overboard with the cutscenes and I wasn't big on the Old Snake thing
Metal Gear Solid 5 - Good gameplay, very mid story by MGS standards though
I might have a little nostalgia bias for MGS 1 since it blew my mind when I was in middle school. Really need to go back and finish MGS 5, I might move it up.
Haven't played any of the portable games, but I've heard Peace Walker was good. Haven't played the NES games either.
Metal Gear Solid - Classic
Metal Gear Solid 3 - Classic
Metal Gear Solid 2 - Great, although I'm still mad about having to play as Raiden
Metal Gear Solid 4 - Good, but they went a little overboard with the cutscenes and I wasn't big on the Old Snake thing
Metal Gear Solid 5 - Good gameplay, very mid story by MGS standards though
I might have a little nostalgia bias for MGS 1 since it blew my mind when I was in middle school. Really need to go back and finish MGS 5, I might move it up.
Haven't played any of the portable games, but I've heard Peace Walker was good. Haven't played the NES games either.

sounds like it might be worth it