Yes, you can say Avengers was bigger than Avatar, because it was. It made more money. That's how box office works.
What do you mean by "Marvel films made more money but they weren't bigger". That literally means nothing.
I'm aware that the numbers don't include inflation, but for example DH1 made 660M, Avengers made 900M two years later. Does the rest of the world have a 40% inflation rate in two years? Hmm.
Why does it matter that it wasn't in China? Like literally how is that relevant. In some markets Harry Potter is bigger than MCU and Star Wars, in some it is not.
But overall speaking, internationally, overseas, both Avengers and Star Wars make more money. Simple as that. Sorry.
Might also mention that Fantastic Beasts had China and it doesn't change anything.