I don't think many people in the comments understand how sharing a console really works lmao.
The game isn't "his" he payed for and downloaded it onto a SHARED console. I don't think he has a right to decide how you use a console that you two share. It's not like you can "buy your own copy", you can't load the same game onto one console more than once.
To make it easier for people in the comments to understand: it is basically the equivalent of sharing an MP3 player and taking it in turns with your friend. Your friend downloads an album onto the MP3 player but then demands that you can't listen to "his" album on your SHARED MP3 player. It's childish, dumb and doesn't affect his enjoyment at all. Apart from the childish perspective that he wants to "play with it first".
You playing the game has no affect on his enjoyment of the game so long as you're not telling him spoilers. He sounds like a brat and his reasoning of "I want to play it firsts it's my toy".