Endgame is the culmination of a 10 year story. Infinity War was an event movie, where even casual fans eventually went out and saw it. Now they want their answers ASAP.
The closest thing will be Episode 9, because it ends the "Saga" - but it's also not the last Star Wars movie. Once the trailer comes out, all doubts because of TLJ will be out the window (Unless it somehow looks terrible.)
Avatar 2 will have some hype - but I don't think it'll match either SW or the MCU. The first one had the hype of Cameron's first movie in a while, and it was an original story, plus all the tech and 3D that it was revolutionizing. Some of that shine will not be present for #2.