I predict that Rockstar Games' Red Dead Redemption 2 will be the top selling game of Q4 2018 therefor beating the new COD, Battlefield 2, FIFA etc. 

Which game do you think will be the best selling game of Q4?   

Highly possible but FIFA/COD are strong contenders as well.

If the bext CoD is either BO4 or the rumored Vietnam CoD, then RDR2 has no chance of selling better. 

Probably. God the mainstream industry is so tired.

If pokemon doesn't come out this year. I'd say its a given. RDR 2 cant come soon enough!

Only if the next CoD is another Infinite Warfare level flop (by CoD's standards) and EA badly botches the next Battlefield and FIFA. But I guarantee there's no way FIFA is slowing down in sales this year, because this year is THE year.

I think while RDR2 will outsell them all eventually, i still think COD and FIFA will outsell it this year. I hope i am wrong though

Highly unlikely.

We'll get the usual crowd who buys it every year and we'll get some additional purchases from people who are going to be in that Futbol State of Mind and won't be satisfied with just the World Cup. It's the most popular sport on the planet, by far. And the World Cup is the "End All. Be All." of the sport. Expect EA and Sony to take full advantage of that.

Ask me after E3.

It very well could be, but we have to take into account FIFA and CoD, not to mention the possibility of a Pokemon on Switch. It is still unconfirmed, but all signs indicate a pokemon release on Holidays, whether it's a mainline game or not.