I am making a game like GTA.Its called San Fransisco gangstars.I am making a games based in Northern California.So i have a team of 10.I am asking how many days would it take to make a game like this?
Well, GTAV took something like $100 million plus about 5 years, so what do you think?
We’re going to have to start calling you the dreamkiller soon Darth with your daily dose of reality.
Or maybe Captain Realist 
It depends on a lot of factors how much time it will take. To name a few, experience/skill of team and their dedication towards the project are big ones. You should read this thread about a very similar project taking place. These guys have about the same number of people at the time this was posted. According to the post they’ve been working on it for several years now so unless you are in it for the long run, I’d start out with something smaller and build your way up from there.
I’m happy to have that designation–I have to say though, when I first got started in 3D I had one of those terrible/impossible ideas so I think most people do that when they first start out and don’t know any better. My experience was very cringe-inducing, I’m glad it was like 15 years ago
Aha yeah I know what you mean. We’ve all been there with the impossible unrealistic first idea, probably how most of us started out 
Reality is a ***** .
But to the OP, don’t think I’m mocking you good luck to you and I hope you do make something. Just be advised of the reality of making your idea and bear in mind we read a post like this on a daily basis so the first reaction from us is usually cynicism
You forgot to mention how many people worked at GTA5.
and realistically it’s probably more than $100 million
Just remember though that OP never specified GTA5. For all we know he is talking about the first GTA which would be a much more obtainable goal.
Jimandy, I am going to guess you are new to UE4 from your very first post, and new to game development from what you wrote this thread. Your question, the way it was asked, with the limited info attached, is a question pretty much only a person new to game development would ask. (I can expand on this if anyone asks why I would say that) Its perfectly fine to be new to game development. I am new as well, in fact.
The reason why I mention the fact that you are likely new to game development is because your game idea is HUGE. If you are talking about GTA Five, you are talking about DECADES of work, if its split among 10 people. Now, maybe you mean without a lot of the content in that game. Do you want five main characters with different voice actors? Do you want a massive variety in the types of cars, and NPCs roaming around? How many voice actors are you going to get? Do you want the radio stations in cars with a huge amount of just extra content to listen to? If you can live without those things with your group of 10 developers, you’ll shave years off your time, but that still doesn’t make it feasible likely.
So to give you more advice, answer these questions:
-
How much experience do you have making games? - If the answer is “very little” then the advice you are going to get from every person here is going to be “start MUCH smaller”.
-
Describe your team of 10 in more detail. Are they already all onboard? How knowledgeable are they? - I will tell you that probably everyone here with a fair amount of game development experience is guessing that this team is NOT a cohesive group of developers experienced and motivated enough to stay together long enough to come close to making a game like you are suggesting. I would further guess most people here are suspicious that the team een currently exists at this stage.
-
Describe some of the major features of the game that will affect development time: Multiplayer? Voice Actors? Sand Box game? Single player story? - Again, if you are new to game development, the answer will be to start much smaller.