CoD is on decline, and has been for some time. Battlefield 5 will do better than CoD IMO.
As for which will sell most? I am going with Smash because the Switch is a hot item right now and that is the next big game on the horizon that we know of. Fifa could take it though due to being multiplat. Red Dead 2 and Battlefield 5 will be a near 3rd and forth.
Just my 2 rupees.
Bet Shiken that COD would outsell Battlefield in 2018. http://gamrconnect.vgchartz.com/post.php?id=8749702