Grand Theft Horse 2 did well its first week. About double the numbers of the previous game, leaving this at over 500k for the week, but still only 27% of GTA V. And BOY is that split nasty. MS tried to move all the consoles they could with this game by undercutting Sony's marketing deal, but the result remains the same on the current trend. A bigger split than Blops 4 by quite some margin. Couldn't take out FIFA though.
Rockstar told share holders this wouldn't be as big as GTA, and that's reasonable. Hell, at least R* bothered to make another game, since they seemed content in soaking up Shark card money. But, still the biggest non-sport title debut of the year for the UK.
I expect a much larger debut in the states being that Westerns are most appealing to the US market. With over 3000 people working on this title, this was probably Rockstar's biggest game yet. Hopefully for them it'll have some legs.