This means it has outsold Xenogears, and every other Xenosaga and Xenoblade game.
Xenoblade Chronicles 2 is a great game. It has its fair share of issues- quite a few of them, to be honest- but its highs are so high, they more than make up for it. The game has managed to resonate quite strongly with a lot of people- as of December 31, 2017, we knew it had sold over a million units in a month.
Now, per Nintendo’s latest financial report, we know that Xenoblade Chronicles 2 sales worldwide stand at 1.31 million units, which indicates that the game has continued to sell over the last three months- this, in spite of JRPGs being front loaded, and the first quarter of a calendar year being the slowest period for game sales. Xenoblade 2 is now Monolith Soft’s highest selling game of all time- this counts not only the other Xenoblade games, but also all the Xenosaga games, and even Xenogears.
Given how well Monolith has continued supporting the game since its launch, and that major new content is in the pipeline, for free and also as paid DLC, this game may just end up having a longer tail than JRPGs often do.