Having said that; there is plenty of diversity in this game. The visits to the shops. The things you do back home. The collecting. The cutscenes. The minigames. It is not only the actual missions. If you look at each individual part of the game, those parts can seem repetitive. But when it all comes together there is plenty of diversity.
I think all games are repetitive to a big degree anyway. Fans of the myriad of FPS clones (Fallout, Resistence, Call of duty etc) should not even start debating. I think a game like 'Gears of war' (a very popular game) is more repetitive than NMH. 'Gears of war' has no minigames. It doesn't encourage exploring. You are given a few options on which way to go but it really is very streamlined. But this is still the most popular game for the 360. And I also think it is a really fun game to play. I actually put down 'Gears of war' to play another game that is all about being repetitive: 'Rampage: Total destruction'.
So, I am not making excuses for a boring gameplay by saying that I think this game is art. I really find the game fun and diverse because the contrast is so big between the old-school gameplay and the twisted and intriguing plot. No other game I know offer the same kind of experience.