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.

Then how do you explain that Last of Us has sold over a million units more than any Uncharted game yet?

That's quite easy.

First of all TLOU has had larger customer base (PS3 + PS4) and has had 2 separate launches, notice that on PS3 Uncharted 2 & 3 both have big lead over TLOU.

Second point is the down fall of Resident Evil and other former great survival horror series, which lead into a demand for a proper game in that genre. I'm trying to say that it is the new king of survival-horror

Third point, demand for new games for PS4, this section includes people that passed TLOU on PS3, people that rebought it for PS4, and people that moved from Xbox 360 to PS4. (I'm one of those people that skipped it the first time, I got in a PS4 bundle which also included Driveclub and LBP 3. Great game by the way. =D )

TLOU 2 doesn't have the same advantage (2 platforms) over Uncharted 4 as the original TLOU had over Uncharted 2 & 3

But what gives the edge for Uncharted 4 then? Uncharted is easier to market, has more action and more potential to grow, in other words it is easier to access for casual gamers which form the majority of gamers. 

The potential sales scale could go like this: FPS=GTA > Action > Survival-horror = RPG > Fighting > JRPG

"Uncharted 2 & 3 both have big lead over TLOU."

The PS3 version of the Last of Us is tracking much higher then Uncharted 2 and it was keeping up with U3.

Can I have official numbers from somewhere? I'm drawing my conclusions on OP's starting post charts. :D

www.vgchartz.com/tools/game_comparison.php?reg=Global&ending=Cumulative&game[]=Uncharted+2%3A+Among+Thieves+(PS3)+[28733]&game[]=Uncharted+3%3A+Drake's+Deception+(PS3)+[49054]&game[]=The+Last+of+Us+(PS3)+[70350]&game[]=

As you can see The Last of Us is clearly selling at a more rapid pace than Uncharted 2 while it was tracking closely to Uncharted 3. This of course does not include the PS4 version. Additionally, it is widely suspected that TLoU is significantly undertracked on the PS3 but that is a matter for another discussion.

So are you saying that TLOU is undertracked by a million? This chart only proves my point, TLOU momentarily surpassed Uncharted 3 in weekly comparison because of Christmas sales, but Uncharted 3 regained the weekly lead with its second Holiday bump. And the reason why it looks undertracked is because of the differing release dates Uncharted in October/November and TLOU in June. So the curves don't quite match.

Now you may say that the PS4 version terminated a lot of the PS3 version's Holiday sales this year, which might be true... partially. "Partially" meaning that PS4 is a lot more "sexy" Console and it is a lot easier to sell 2+ million on PS4 than on PS3. Just look at GTA V on PS4. Even mediocre games like Knack can reach 1 million. So nobody can just add the PS3 and PS4 versions sales and say that TLOU would have sold more on PS3.

Of course I could be wrong about everything and TLOU is horribly undertracked, but until I have solid proof on my hands UC2 & UC3 both have sold better on PS3. :)

bolded: Actually, yes. At least a million. The PS3 version has shipped 7 million as of April 16th at the point vgchartz has the game at 4.75mil sold and I think nobody really thinks that this game still had over 2 million units on shelves 10 months after release.