I suppose that Domm 1 is not a problem while Doom 3 is not possible
The main issue however is not the game engine itself
Assuming that you work alone in your free time,you can not expect to achieve the same results of a full time professional team.
The golden rule you must bear in mind is

I must not reinvent the wheel

That's why I came to the conclusion that 3dsg is one of the best 3d game engine even though it is not definitly the most advanced one (forget Doom 3

so what is small
if its a fps first person shooter that you move the gun with the mouse thats harder because all doom is just like space to shot theres no aiming at all