I believe Nintendo and Potter are arguably the most "evergreen" franchises Uni has. Mario is one of the most iconic characters of all time, having some of the most beloved and revolutionary games ever under his belt. He's right up there with Mickey Mouse himself. Potter is one of the best-selling book franchises of all time, considered a classic by nearly all and has proven itself to be much more than a mere fad. There's a reason these two franchises are being chosen to get huge-scale lands that are going to stay for a long time if not forever, while things like F&F and Fallon are getting just rides. I'd also argue that Seuss and JP could be pretty "evergreen," but their existing lands need some serious work to feel higher quality and up-to-date.
And that "evergreen" quality is important, as that's actually an advantage Disney has. Almost all of their animated movies are timeless, Star Wars and Toy Story are huge series, and most of their original attractions work "forever" as well. While I'm not trying to dis Universal, a lot of their attractions do feel outdated. MIB and Mummy for example are great rides, but them being based off IPs that haven't been popular since the late 90s/early 2000s makes them products of their time that will, like it or not, eventually need to be replaced. That's why it's important for Universal to get more and more timeless properties like Nintendo, Harry Potter, and hopefully Lord of the Rings down the line.