Xenoblade 1 was the first. As JRPGs were struggling in the HD age it benefited from being competent and not weighed down by AAA insecurities the same way Final Fantasy never recovered from the tailspin XIII sent it into.
Xenoblade 2 smartly keeps the weight off the job of being a sequel up until its grand finale with the reveal of XC1's final battle happening in parallel. It also doesn't make it a grand revenge quest with a destroyed hometown like XC1. MC meets a mysterious girl and goes on a globetrotting adventure. Classic JRPG stuff. It keeps it breezy and fast-paced and that's why its cast had the most sticking power even outside of Pyra and Mythra being pornbait. The combat system is expanded with the blade system, defined enough to not get into the weeds, but has enough depth to be interesting for people to break it.

XC3 tries to do too much. Everything is designed around its six man team so it immediately introduces them all at once so everybody is immediately trying to vie for space and attention from the plot. It dumps the class system on you from damn near the outset but doesn't have enough variety at first to make all the switching worthwhile. Plot also basically throws all its shit at you at the starting line, complete with requisite Proper Noun spam, while XC1 and 2 at least let you find your footing and play around for a while before letting her rip with the big cosmic war at the heart of all things.