For me there is a big difference between Ronaldo and Beckham. All those times Ronaldo went on about his boyhood dream to play for Madrid, when Beckham talked about his boyhood dream, it was to play for us. Beckham is a product of our youth system and he has been unwavering and categorical in his support of United ever since he left. Ronaldo has been diplomatic since he left but it is not the same thing.
Plus, on a completely different level, Ronaldo is still at the top of his game, is one of the world's best players and could completely destroy us. I think we need to be mindful of that, while being respectful. Becks was well past it, we had nothing to be scared of with him and could afford to be enthusiastic in our welcome, without it coming across as desperate or sycophantic.