The final scene is a very stereotypical geek-boy-gets-geek-girl moment in the garden. If that was the intended ending, boy was it clumsily built up to. He was a fanboy of hers in the first scene, he fell in love with her endearing physical difference when he did get to see her, and she specifically spurned him so that they could both move the plot along. She was a Mary Sue in a world full of them. And that's where I think there was a giant flashing opportunity to say something actually interesting about these characters was missed.
Art3mis should have been artificial. She should be part of the hunt, created by Halliday to ensure that the first person who unlocks the first key has a companion that will spurn him, the same way he was spurned. Not only would the Egg Hunt be causing solvers to follow his cultural history, it would force the one most likely to win to follow his personal trajectory too. Halliday created a virtual reality, now he wanted to craft someone's actual reality. None of the early text would need to be changed! Not the knowing glances as Og said that she'd meet him after they were done, not the dancing, and not a word of personal history. But instead of going out to the garden, Parzival would be led down to the basement of Og's castle, where he would be introduced to a supercomputer nearly as large as the one devoted to the game world itself. This would be Halliday's true final project, an artificial personality to enliven the artificial world. A Queen for the new King of OASIS. Og would have been completely creeped out by it, tending to a virtual version of his dead wife, but it would be baked into Halliday's will. And now Parzival would have a truly interesting choice: become the man Halliday wanted, accepting the virtual as the only true world of any meaning to him, crafting his castles in the Cloud, or to turn back and meet Aech again, seeing her in a new light, deciding that there was something real about reality worth preserving.
If you really liked the book and will re-read it, try it with my head cannon instead of the actual ending. Let me know how it fits.