Can't make object follow mouse cursor position.

I am trying to get this object to move with the cursor on a 2D axis.

(It’s the red cross hairs). This is the C# script I made for it:

using UnityEngine;
using System.Collections;

public class Player_Curser_Movement : MonoBehaviour {

	// Use this for initialization
	void Start () {
	}
	
	// Update is called once per frame
	void Update () {
        Vector3 temp = Input.mousePosition;
        temp.z = 5f;
        transform.position = temp;
	}
}

I had it print out the x, y, and z coordinates of the object, when my cursor was over the center, it said the coordinates were around: 436, 244, 5. When my mouse is in the bottom left corner of my screen it puts the object around the middle of the screen, but it’s very sensitive to movement.

any input on the screen is defined by pixels & object in unity move by points so if the screen width is 800 then the middle will be 400 so you are sending the object 400 point away where if you see by your self the screen width is sometimes 4 or 6 or whatever so as @markpollard1 said you have to convert the input click or touch from pixels to points .

void Update () {
		Vector3 temp = Camera.main.ScreenToWorldPoint(Input.mousePosition);
		temp.z = 5f;
		transform.position = temp;
	}