No, it is definitely more gameplay-driven, which is to say that most of the content and appeal revolves primarily around the gameplay. The sheer amount of missions and play time you can get out of the game, without ever replaying the main story, eclipses the other games. MGS2 Substance probably tops it, though, so maybe not the most gameplay-driven, but definitely the top tier ofMGS. I have played every MGS game numerous times, more than almost anyone here, so I know where the appeal lies in replaying. It holds just as true in PW as any other game, especially with grades at the end of missions. The pacing of the story also isn't broken up unless you choose to do side missions as they come. They're never required to get to the next story mission.
As far as MGS4 is concerned, the stealth in the game is the weakest of the four by a rather wide margin. The design of the encounters is very poor, and even on Extreme is far too easy to get through. It's because the AI is the same, but now Snake is far more capable and the environments are far larger. MGS4 is a better third-person shooter than a stealth game.
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"When I was a young man, I had liberty, but I did not see it. I had time, but I did not know it."