What quality are you seeing that I am not? Also, lighting is going to play a big role. You need to setup the lighting inside unreal to match whatever software you are using if that is the result you are seeking. What software ARE you using exactly?
I made the mesh model by photogrammetry software called Pix4D.
The first and second picture are the view of the mesh model in Pix4D.
The third picture is the view that I just input the fbx file which is generated in Pix4D to unreal 4. I think the mesh model which is viewed in Pix4D is better. Do you know why the mesh model in unreal 4 cannot be similar with what I see in Pix4d?
I am not familiar with Pix4D software, but like creating assets in any 3D Software, you will want to optimize the mesh so that has the lowest poly count possible while maintaining quality. Likewise, with the texture/materials they need to be in a format of a power of 2 (256x256 pixels, 4096 x 4096 pixels etc.) at the lowest size possible while maintaining the quality resolution at the distance they will be seen from.
That said, if your materials are correct when exporting from Pix4D, make sure your render settings are high in Settings at the top of the Editor window.