It's very telling that my favorite part of MGS4 is when you play MGS1 in it. MGS1 will always be my favorite in the series, MGS 4 was a big disappointment for me.
I loved MGS4, I almost felt compeled to give it a perfect score when I finished it, that's how much I liked it.
I actually like 4 more than 1, but none can hope to reach 3.
MGS3 is so good it hurts.
2 is the black sheep of the bunch, it's still a good game but boy it's nowhere near the others.