Pokemon X/Y first week - 4,057,836 million copies sold worldwide.
Pokemon Sun/Moon first week (aligned) - 3,400,000 in Japan and Europe alone.
Well, I think it's a safe bet that Sun/Moon had a bigger launch that X/Y at this point.
Hardware Comparison Threads:
Current Thread
Is Hardware Getting TOO Powerful?
Older Threads:
PlayStation/Xbox/Switch: 2022 Edition
PlayStation/Xbox/Switch Hardware Battle: 2021 Edition!
PlayStation 4/Xbox One/Nintendo Switch: 2019 vs. 2020
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2017 vs. 2018
PlayStation 4: 2015 vs. 2016 vs. 2017