Absolutely great sales, even more when you consider this is a new IP and previous games made by the developer didn't sell nearly as well as this one.
What are the biggest new IPs this gen?
Biggest exclusive new IP for each console.
Horizon Zero Dawn (PS4) - 7.6m
Tomodachi Life (3DS) - 6.14m
Splatoon (WiiU) - 4.91m
Titanfall (XBO) - 3.1m* (Also on 360/PC....)
1-2-Switch (Switch) - 1.88m
Tearaway (Vita) - 0.69m*
Biggest new IP's combined platforms:
Destiny (PS3/360/PS4/XBO) - 16.2m* (includes Taken King)
Middle-Earth: Shadow of Mordor (PS3/PS4/360/XBO/PC) - 9.96m* (Also used steamspy for this figure, 4.4m on steam)
Watch Dogs (PS3/360/PS4/XBO/PC) - 9.58m*
Titanfall (XBO/360/PC) - 5.07m*
*VGC Figures, physical only
Overwatch is probably very high if not at the top of the list, but can't get PC figures which no doubt make up the majority of sales for that game, over 6.2m on console.