I will be very negative about Nintendo, but I think one of the reason they would not benefit from it is that there are too weak to compete. Even on a losing Wii U, they can bundle TV commercials for console and games, start development 1 year ahead of anyone, think about controller usage years ahead, have a predominent share and excellent visibility on their own console, diminish 3rd party revelance by unpowered hardware where their own games shine, have an "exclusivity" label, and sell to a public that owns only nintendo system for years and have no idea or interest for anything else. With some luck they can even get millions of casual with mostly no other gaming experience. They definitely get some kids whom parent decide (I would do the same, Nintendo guarantees your kids will not meet undesirable content). On any other system they would have to compete fiercely with many other companies and licenses, based on pure game value, and even their core user base would be at risk because they would be able to chose for the same price between a massive game like GTA 6 and yet-another mario tennis.
On a more positive note, they build the most affordable hardware and they can define the gameplay and specifications that fits their game the most, I think that's quite an advantage. In particular, by slowing the pace of system evolution they can focus more on games rather than technology (like building a totally new engine because the hardware is totally different and 10 times better).
Also, not only for Sega but can you see a company like Square ? They were at their greatest point when exclusive to the Super Nes and then the Playstation. Did going multi-platform added anything, they are not even selling more... Then, is the extremely multiplatform EA really doing that better ? Their only game that made people talk for years is their xbox one exclusive Titanfall.
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