I played and beat MGS1, 2, and 4. For some reason, even though many say it's the best, 3 just didn't grab me. Sometime last year, I bought the MGS collection, which has 2, 3, and one of the PSP games ported and all upgraded to PS3. Re-played 2 and got far enough into 3 that there was a STUPIDLY long cutscene that I swear lasted 45 minutes. You were supposed to rescue some dude, so I snuck in and was rewarded with 45+ minutes of exposition. Gave up on it after that.
MGS4 was the most irritating. Like other cutscenes in the series, I was left not playing it but sitting and watching with my chin resting on my hand thinking, "Gee, some of this super cool stuff Snake is doing would be sure fun to PLAY." Not to mention the ratio of cutscene to actual gameplay is staggeringly unbalanced.
I'm not even bothering with the series anymore. Been tempted to try Revengence, despite it's really stupid name.