I never really could get into the previous Metal Gear games, but I enjoyed Metal Gear 4 and played all the way through it (I read up on the stories from the first 3 before playing). It plays more like a shooter than the others.
Obviously, you have to be willing to endure some long cutscenes. Personally, I enjoy cutscenes (that's why I love final fantasy) and appreciated the movie-esque presentation values of them. But even for me, they dragged on a bit too long at times. For me, it basically went up and down. The opening was cool, Act 1 was boring, Act 2 was good, Act 3 was freaking INCREDIBLE and if it kept going up from there it would really be one of the greatest games ever like some people made it out to be, but after that it really kind of fell apart in Acts 4 and 5 for me. Everything just got kind of absurd, especially the plot, which is capped off by a little over 2 hours of convoluted cutscenes.