GTA V is a remaster of a multiplat game that came out a year ago and sold so well that few owners of last gen consoles that buy at least one game a year don't have it, and most of those who do have it won't likely drop another $60 on a game they bought for the same amount last year, especially in a time of the year when there are other, newer games coming out almost every week.
Halo is a remaster of four games that are staying exclusive to a single platform brand that (for the most part) are old enough to garner huge amounts of nostalgia for those who played them and as a result huge amounts of internet hype, so much so that people who have only played one or two Halos are interested in picking this up to play the other games they haven't played.
Add to the fact that GTA V doesn't seem like it will be marketed for shit while MS will likely advertise MCC as much as they can, and you can easily see that MCC will sell well whereas GTA V will do well, but not really groundbreaking levels. Keep in mind that Tomb Raider: Definitive Edition launched in an otherwise empty month and
only did 85k. I expect GTA V to do 100k-ish, but I don't think it'll push consoles really any hard or anything and it definitely won't be near the top for that month. MCC, on the other hand, IMHO has the potential to do 200k-ish+.