Xenoblade Chronicles sold 161,000 units by the end of 2010 in Japan. What isn't mentioned is the Western sales.
"In a later interview, it was stated that [Xenoblade Chronicles] sold better in the West than in Japan." We can conclude from this that the game sold at least 400,000 copies worldwide, since it had sold 200,000 copies by the end of 2013. That's over three years, mind.
Xenoblade Chronicles X had sold 114,665 physical copies by the end of the year, which doesn't account for the 23,000 digital copies during May 2015. Together, that accounts for 137,665 copies by the end of 2015. This is not counting digital sales for June, July, August, September, October, November, or December.
In the west, it sold better than the original did. "Upon its release in the United Kingdom, the game managed to secure 28th place in the charts. Despite its modest position, the game's launch sales was 73% higher than its predecessor had been in the same region," and "In the UK charts, Xenoblade Chronicles debuted at #7, and reached #2 in the dedicated Wii charts despite stock shortages." "In France, the game sold over 40,000 physical copies after two weeks." "In the United States, the game sold over 200,000 physical copies during the month of December, nearly doubling the game's then-lifetime sales in Japan."
Considering all of this, Xenoblade Chronicles X had sold 377,665 copies in 8 months, not counting digital copies, UK sales, Canada sales, non-France EU sales, or South American sales, which the above figure does include. Odds are that the game had matched the original's lifetime sales in 8 months when one considers these.
"Monolith Soft posted financial results for the fiscal year ending march 2016. Total profits were 2.7 billion yen, an increase over the 1 billion yen reported for the last FY." This also means that the game continued to sell well after the NA release in December. At the very least, the game reached half a million by 2016, which beats out the original game.