Hmm..
Well as a PS player the only thing that's made me want to play on Xbox has been the small exclusives like Rivals of Aether (look it up) and Speed Runners.
Maybe show him that?
Also I have to inquire (I'm so intellectual) why not get a ps4? You could be the one to make the switch.
Edit*
Halo 5 multiplayer looks fun.
English
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H5 mp is fun. Super super fun
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I have an Xbone right now and don't have the money for another system.