You do realise that the only game to have ever broken 15m barrier (one console) that wasn't a new ip is GTA correct? And that only happened after it turned to a completely 3d world, so was basically like a new ip anyway. 

The most I see it selling is 12m, and even that is doubtfull 

TLOU is bigger than Uncharted now I think.

TLoU (PS3) is still horribly undertracked that it hurts.

The Last of Us 2 will probably sell more since it's going to have the benefit of a larger install base and the first one did so well for a new IP.

I'd say Uncharted 4. It's the last game in the series (apparently) and by the looks of it each new entry has sold more than the previous. Not to mention the graphics will make some people buy it cause graphics.

I somehow don't see TLOU2 do as well as Uncharted 4. Not sure why, it's just a feeling, but some games only work once.

TLOU2 will sell more.

Both will sell great numbers, U4 will be the highest selling uncharted game due to the critical reception of the previous games and not to mention how ND become a prestige studio after the last of us, which is their best selling IP now. The last of us 2 will be even bigger than U4. Anything is possible and both are quality games.

Uncharted 4 hands down!

Why? Because TLOU is more like a survival horror game, rather than an action game, so it is automatically less attractive option.

Why do you think that COD or FIFA sells always good regardless of the quality? Because these games have easier accessibility.

Uncharted is more on the action side when it comes to the gameplay: lots of satisfying shooting, some problem solving etc. 

TLOU on the other hand is a game where every move has to be planned, you can't just go guns blazing at clickers and you have to save your ammo for the worst situations.

It may look like TLOU would have more room for market expansion, but that is because the survival horror genre in general has gone into a slump, and once people find that one gem among all of those Alone in the Darks and Resident Evil 5s and 6s it will automatically gain instant fanbase.

However TLOU is a niche game and even though it is a great game, majority of gamers won't like it. 

Uncharted on the other hand is easier to chew and even major fans of COD & GTA can find it somewhat satisfying.

I would say TLOU 2 because the base would be much bigger by the time it hit.