It's a bit of a silly comparison considering
1. Halo's decline as a system seller
2. Halo 5 isn't exactly a mainline Halo game
3. Install Base difference
4. Vgchartz don't seem too accurate in XBO game sales. Why I don't know.
It's a good achievement for UC4, but i doubt Uncharted 4 will ever outsell Halo 3 or 4.
While it is a good achievement for UC4 to reach that number; that^^
Esp 3 and 4...
We know as a fact that Xbox One digital numbers are high and they are not taken into consideration and they are way bigger than what VGC is capturing.
Like mentionned multiple time just Bing about it if are still unaware of that :)
Also, it shows again how Sony's exclusives are not selling as much as Microsoft/Nintendo (esp. Nintendo actually) for a comparable user base. The install base is the double and it barely beats it (even with innacurate Xbox One numbers)