In most games, there is only one maybe 2 major bosses. I am going to go with a few more major bosses. The reason why I am saying this is because I am tired of the 1 major boss fight and then the game ends when you beat him. Well Pretty much it does. But what if you have to deal with four of them. Yes it makes the game harder and more scarier. Because you got more of them to deal with than you like. And the bosses will follow you from time to time. But not every where. It would be as if they was pushing you towards some one or some thing maybe in another part of the city. Yes by having four bosses it makes the game some what boring, but then again I think it adds to the fear factor. Think about this, your in a huge city and you know that you got a few smaller creatures to deal with, but the character doesn't know that there are bigger and much meaner creatures out there. That just happens to be waiting to rip them apart. I just want the players to feel like there is no way out and that they will die in the end. Basically speaking the player / characters will be in danger every step of the way. And that there is really no safe haven in the entire game. Think about this, your being hunted down and your looking for a safe place to hide or heal (depending on the situation and health of the player) and there isn't one to be found. So you are constantly feeling the fear of dying. Which is good. Because it adds to the scareyness of the game. Like an impending doom type thing. Getting back to the bosses, they will chase and follow you but only for so long. Of course you know that they are tougher and will require more powerful weapons and shots. So surviving the game becames that more tedious. Any ways the bosses are the creame of the crop. They are the meanest things that are in this game. And the fact there is four of them, means that you won't have much time to stop and rest or heal. Since some of the bosses actually follow you, I am allowing the player / character to have hiding areas to wait in until the boss leaves the area. But these hiding spots won't be good for long. Anyways the bosses and their lower counterparts are always looking for you. So you will need to either kill them when you get the time or keep running. Also I would like to add in there is a special weapon in the game that can kill the bosses but it is not a rocket launcher. Any ways the bosses will still require several hits from the weapon before dying. In the end you will see that they are not a cake walk and will do any thing to make sure that you die. As for their intelligence. It is quite high and they will from time to time out maneuver your players attacks or shots. Making them much harder to hit and kill. Plus they have one attack each that is virtually impossible to evade or block. And this one attack leaves your player with half a life. In the end I hope that you all see that more bosses adds to the fear factor of the game. And if people don't see this point of view, that is ok.. Because all this is, is my opinion and I know I will see other opinions and I am cool with that.

What kind of game will it be? 3D like silent hill? FPS maybe?

To be honest it will be like silent hill and resident evil. You will be able to see the whole character and I want to go 3D. But since I do not know any thing about stuff like that, I am trying to find some one who can handle that aspect of the project. I wished I could answer it better. But like I said I don't know any thing about that kind of stuff. I know this probaly didnt answer your question, and for that I apologize. There is things I that I know about, but this is not one of them. Laughing out loud. But I wished I did.

My friend and I who are making a horror game we have like bosses and that but what do you mean they folow you? like if you encounter them lurking around and they see you the are like "oh cool a little thing to eat" and they chase you or are they boses at the end of a level or chapter?

Sounds like Ecstatica.
Its a really old game but it had something like this.
There were some strong monsters in the game but you couldnt
beat them until you got the strongest weapon iirc.
Sometimes they would jump you and you would have to run away.
It was fun but a bit annoying at times.