The Uncharted games sold about 5-6 million each, one one platform. Since then, ND's brand has only grown, with TLOU well on it's way to 10 million (albeit on two consoles). By the time UC4 comes out, the PS4 will have easily crossed 25 million, and it'll be close to 30. ND is Sony's premiere studio, which means they're going to be pushing it hard, plus it looks friggen amazing so there will no doubt be tons of hype (not to mention, it's supposed to be the final game).
Halo 5 comes on the heels of a disappointing Halo 4, on a console with sales that are less than impressive. By the time it comes out, the X1 will be lucky to have crossed 15 (maybe it'll be at 16 or 17 million). While there will certainly be a lot of hype, I feel that all these factors will combine and lead to UC4 outselling Halo 5. Especially since Sony now holds NA as well, which means they have an audience that they may not have had last gen (a lot of 360 gamers switching over) along with their established base.
TLOU2 will be even bigger.