AFAIK as I see, no one is "defending" anything, just understanding... i.e.: If Sony could exploit a single franchise as Nintendo exploits Mario, they would with no hessitation, it's just that they can't, they create more AAA IPs because the ones they already have don't last as much as they wish they do.
Probably has something to do with franchise fratigue, Nintendo has one 3D Mario per generation, whereas Sony had 3 Uncharteds on 7th gen. Even Gears of Wars went from system seller to "meh" probably because of the same reason, same happened to Assasins Creed.
Tho, Nintendo just have the formula for creating IPs that sell, not of them sell but when they do, they're a massive hit or sell above average (Splatoon and ARMS come to mind)