If reports are true, NX will be the first handheld console capable of uncompromised modern gaming on the go. Open World experiences like GTAV, GTA online, Skyrim and MMO's like FFXIV can be run on the same portable device that you play Pokemon RPGs. Could remastered ports of these games sell huge amounts on the NX? 

Imo, no, because I don't imagine that the bulk of gta fans play on handheld to begin with and wouldn't unless something like Pokemon go came around.

GTA is casual but it's older casual. Same audience that the vita was initially targeted at, and... Well... I don't think it'd be a game changer. For Nintendo they have their IP that will work its magic on winning over the portable market. Gta isn't necessary

No. I thought gta on the psp was gonna be huge but it didnt do much

Every game you listed was released for last generation devices... And chances are. Played to death by millions already.
Don't you wan't new gaming experiences rather than old ones?

GTA V on the NX would be a system seller for me, I've been wanting to play a real GTA game on a handheld since VCS in 2006.

It would also sell very well. Nintendo only owners will get a taste of this great franchise, and I'm sure people who played GTA LCS and VCS on PSP would want another GTA game on a handheld. LCS sold 7.5 million and VCS over 4.5 million on PSP if I remember currently, and GTA V remasters do really well so I think it has potential to sell millions on NX.

If NX has Tegra X1 they could make a portable version that's much better than last gen versions, run it at 720p with lower anti aliasing than console versions due to smaller screen and enhance visual effects and framerate. Tegra X2 would be even better.

No, the audience for it is not there

It's an old game now.

Does anyone still play GTA V? And stop trying to make Nintendo+GTA happen, it's not going to happen. I'm more excited about a Pokémon with HD graphics than with a HD game on a handheld.

No, because the GTA userbase preffer longer sessions, as supossed to the shorter playtimes of handhelds. And in Japan, when handhelds are the biggest dedicated consoles, GTA is not really big at all, so that's something. Plus, T2 doesn't care about Nintendo in the slightless, so the question is kinda moot.

Nope, because there is no GTA audience on Nintendo consoles.