Compared to before, he doesn't play video games as much as he used to.
ご質問ありがとうございます。
「彼は[以前](https://eikaiwa.dmm.com/uknow/questions/32986/)ほどテレビゲームをしない。」は自然な英文で「Compared to before, he doesn't play video games as much as he used to.」とおススメします。
Kazukoさんの英文もみてみましょう。
「He played video games less than before」より「He plays video games less than before.」の方が良いです。
ご参考になれば幸いです。
He doesn't play as many video games as he used to.
He plays fewer video games compared to before.
この場合、次のような言い方をすると良いですよ。
ーHe doesn't play as many video games as he used to.
「彼は以前ほどテレビゲームをしない」
ーHe plays fewer video games compared to before.
「彼は前と比べるとテレビゲームをする回数が少ない」
ご参考まで!