best game should i get ?

Dark Souls 3! Invasions are fun! :)

DOOM, which is going to be released next month.

Honestly, none of those 3.

https://steamdb.info/graph/?category=1 - here you have multiplayer games and numbers so you can judge which games are alive and which are not

GTA 5 should be your choice

Get Sid Meier's Civilization V :P

If you'll have friends to play with Rust would be an alright choice. But beware official servers are really bad(laaaag) and you can hardly find a stable community server.

Honestly I would just wait a little for Doom.

Awful games are awful.

Maybe Arma 3?

I always wanted to get arma 3 but they keep only having max 50% discount (still hoping there would be 75% or higher discount soon)

CSGO

No Mans Sky ?
If your searching a game for a Loooong run ? =)

Battlefield 4. The community is really big and you will always find servers.

Witcher 3 for single player.

Dying Light or Grand Theft Auto V.

Both has amazing Coop/MP.

I'd go for COD Black Ops 3 because of Zombie Mode, would love to play it with my fiancee.

Those are some mediocre games right there.

I'd say go for Garry's Mod or Dark Souls.