Wow. Came in here expecting a Gaikai thread and got hit by this instead!
It's an interesting subject. Obviously, I'm biased, but I love Sony's first party for all the reasons you've mentioned. I find that a lot of their studios - for a long time now - have followed this sort of 'Cinematic game' mantra, which I really quite enjoy. There's an interview with Jason Rubin & Andy Gavin (co-founders of Naughty Dog) somewhere on youtube who mention that it was always their goal with that company to integrate a gameplay & cinematic experience together, which is something the company partially succeeded with Jak but got much closer with Uncharted.
And obviously, that extends further than just Naughty Dog. Like you mention, Gran Turismo (although not my type of game) has always been a sort of fully-immersive racing sim. Shadow of the Colossus pulls you into its world despite going for minimalism. Even stuff like God of War is incredibly cinematic, and I find that it is to hack & slash as Uncharted is to third-person shooters.
Anyway, I'm rambling now. To get back to your question in the OP - I'm not sure whether Nintendo should do it (and I'm not sure if they ever will), but it would certainly be very interesting to see. Nintendo are obviously very, very good at what they do - and they make sure what they put out is more polished to a fine tip. But a bit more diversity wouldn't hurt - trying something new wouldn't necessarily be a bad idea.
Idk really. I appreciate Sony for their diversity as much as I appreciate Nintendo for their skill at what they do. They've both made decisions I haven't liked this gen, and they could both stand to do things a little differently in my opinion.