Those seem like such random games to compare, but anyways:
R1 A: Splatoon 2 is very popular, but so is Monster Hunter. I honestly have no idea.
R1 B: MHW for sure, just because of how many PS4s/XBox Ones are ou there.
R2 A: MHW is almost being marketed as a PS4 exclusive. I think MHW wins this one.
R2 B: MHW for sure.
R3: This one is really hard. MHW will sell much better in Japan, but Horizon sold much better in the west.
R4: MHW because it's 110M consoles + PC vs 30M consoles.