What Zelda and GTA have in common is they were both really good at being 2D top-down games. After that, I'm not so sure but I could probably draw some abstract comparisons or rubbish someone elses ideas but come on, where's the fun in that. I'm trying to think what the Zelda equivalent of Bully could be but, gah, I'm getting nowhere. Someone else can run with that.
My personal (constructive?) tuppence is that open world games are something I've never really clicked with. I find the lack of direction makes them feel pointless. I think you are supposed to settle into these worlds and get to know them and be happy just to mess about (something I'm content doing in Animal Crossing and Tomodachi Life, for example) but I've never been able to apply that mindset to non Touch Generation games. Yes, there's a story to follow in GTA but the real attraction and fun people get seems to come from killing people in super creative ways.
As long as Zelda U is a wee bit more open world than Skyward Sword, we'll be grand. But then are all the other Zelda games not open world? The more I wonder about it the more I need a definition of open world. Is an open world Zelda just a Zelda without a Kokiri Forest to ease you in?
Does Link need to be an adult. Sure adult Link is just a teenager anyway isn't he. Well excuse me Princess but that's what we call adult now is it?