Sounds like the computer game has become an addiction, so you're not just wrestling with changes in the relationship, you're wrestling with a third party in the relationship - addictions do become third parties - and can be deal-breakers. He may have to be the one that makes a choice between his wife and his mistress (the computer game)...and if he can't make that choice, that will be an important factor in your decision.
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When you don't like a thing, change it.
If you can't change it, change the way you think about it.

(Maya Angelou)