Just like most of the awards ceremony took place in Jan-Mar, both Indian and American, IMO GameAwards should take place in the same period as well so even games which released on 31st DEC, even that can be counted and not left behind.
IMHO RDR2 is the Game of the Year for 2018. GOW is not everyone's cup of tea. RDR2 has more audience. All kinds of people can play RDR2.