The speed of the hard drive depends on the density.
A 5TB hard drive will be faster than a 2TB hard drive. Because you bought a smaller drive, there are fewer heads, fewer platters, and less bit density. All hard drives spin at specified speeds (either 5400 RPM or 7200 RPM), so the only thing that makes things go faster is "bits per inch", so to speak.
Bigger hard drives have more bits-per-inch and still spin at the same speed (7200RPM), and thus have faster performance. By buying a 2TB hard drive, you're naturally going to have less performance than a 3TB, 4TB, or 5TB drive. 200MB/s seems like a 4TB or 5TB drive speed, in my experience. 150MB/s is about right for a 2TB drive like yours.