Xenoblade Chronicles 2 is actually the third game in the Xenoblade series, and the tenth game in the Xeno series by Tetsuya Takahashi. The story behind the series is complicated, and best left to a whole other article, but don't worry. For this game, you only have to worry about the Xenoblade franchise.
Given the fact the game has a "2" in the title, it would suggest that it's a sequel to Xenoblade Chronicles or Xenoblade Chronicles X. Instead, it's more of a spiritual successor to the first two games in the series. Chronicles 2 takes place in an entirely different world than the first game and X, though it shares plenty of similarities with both those games. You don't have to worry about playing Xenoblade Chronicles before Xenoblade Chronicles 2.
Is Xenoblade Chronicles 2 a Sequel?
A lot of the gameplay systems from Xenoblade Chronicles and X carry over to Chronicles 2. The same real-time combat and skill system has been implemented, though there are improvements. You'll still fight as part of a three-person party, and status effect chains like break, topple, and launch can still be executed.
Xenoblade Chronicles 2 also carries the same core feeling as the first two games did. There are vast tracts of land to explore, with powerful treasure, crafting items, and collectibles being found off the beaten path. You can zip through the game as fast as you can, or spend 100+ hours performing side quests and exploring. It's up to you.
A lot of the same themes pop up in the new game as well. There's much concentration on the power of comradery. There's also the idea that humanity hasn't found its place in the world. However, that's where the similarities end. Xenoblade Chronicles 2 isn't a sequel to the previous games.
What's Different Between Xenoblade Chronicles 2 and the Other Games?
The most significant difference between Xenoblade Chronicles 2 and earlier titles is the world is completely different. In this new game, the world is covered in a sea of clouds, and humans live on the backs (and inside of) huge, ancient creatures called Titans. These Titans roam the cloud sea, but there's a problem, the Titans are dying.
As the Titans die out, humanity has less and less land to live on, and this has led to ongoing wars. With resources continuing to dwindle, the main character, a salvager named Rex, finds himself in a world that rewards cruelty and selfishness.
You're also introduced to a new being called a Blade in Xenoblade Chronicles 2. Blades are living weapons which are bonded to humans called Drivers. These sentient armaments enhance a Driver's abilities and are wielded by the strongest warriors in the world. One of the main focus points of Xenoblade Chronicles 2 is the story of a legendary blade called the Aegis and her journey to make it back to where humanity, Titans, and Blades sprang from: Elysium.
Do I Need to Play the Other Xenoblade Games Before Xenoblade Chronicles 2?
If you want to play Xenoblade Chronicles 2, you don't need to play the other games in the series first. You probably should at some point because they're great games, but you won't miss anything if you don't.
Also, if you play Xenoblade Chronicles 2 before the other two games, you won't have any of the stories ruined for you. Besides the scattered reference and similar species, there's nothing that will spoil any moments from Xenoblade Chronicles or Xenoblade Chronicles X.