The user perspective looks "more like realistic 3D objects"? If that depends only on view angles then I'd say you have to change your camera settings. The foremost difference is the Focal Length, I would guess. You can set it differently for viewport and camera.
By default, the 3D Viewport and the standard camera object both have a Focal Length of 50 mm (unless you changed a setting and saved it in the startup file).
Generally you can use Ctrl+Alt+Numpad 0 to make your active camera switch to the view you see in the current user perspective. If you didn't set different focal lengths for camera and viewport, the camera will show exactly the same perspective you see in the viewport.
Let's say your camera shows this:
In the User Perspective, you have a different view on the cube like this, notice that the Focal Length for View Properties and Camera Properties are the same:
If you now press Ctrl+Alt+Numpad 0 the perspective stays exactly the same, only that now there is a frame showing the camera's field of view.
A different result you will get if the camera and the viewport have different settings for focal length. In the following example the viewport stays at the default 50 mm but the camera has a focal length of 120 mm.
If you now switch the camera with Ctrl+Alt+Numpad 0 you'll see that the resulting view looks a lot different than the User Perspective, but have a look at Location and Rotation of the camera:
If I instead would repeat this with a camera like before, which has the default focal length of 50 mm like the viewport, the new perspective would match the viewport - and it has the same Location and Rotation as the other camera.
So using Ctrl+Alt+Numpad 0 doesn't actually switch the camera view to match the current user perspective view, it moves the camera to a position and alignment where a camera which has the same focal length as the viewport setting needs to be placed.
And one more thing I didn't mention before: under Camera Properties > Camera you have settings for Sensor Fit and Size. They should be left at Sensor Fit: "Auto" and Size: "36", otherwise the camera view will differ from the user perspective as well. Since these settings are not available in the Viewport Properties there's no way to match them any other way.
To use this feature, switching the camera to the current view, you would either have to set the camera according to the viewport settings or the viewport to the camera's settings. The reasons they are not automatically matched to each other are manifold, for example you want a dramatic view from the camera but this doesn't work well for editing the objects, to name but one.
If you like the perspective of the viewport more than the one from the camera, you should take a look at the settings and maybe change the focal length. All in all it is always possible to get a "realistic" view with the camera, you just have to find what you're looking for. It is always helpful if you can identify what makes you think the other view is more realistic and then try to change the camera to achieve this.
//EDIT: Just a little addition to the above explanations. If you are wondering why switching the camera to the current view only uses such a small portion of the whole viewport, that's because Blender tries to fit the camera's field of view inside the viewport window - no matter which aspect ratio the render dimensions have. So the area of the camera's view will never be wider or higher than a 1:1 ratio could get to still fit inside the viewport. You can see below how the camera's clipping section always fits inside the 1:1 area, no matter how big or small the viewport is (this is only valid for switching the camera to current view, of course you can scale in or out afterwards).
