The "smooth" modifier would give back the smooth look.After you added this to your mesh, you can check the "auto smooth" checkbox, and you can set the maximum smoothing angle with a slider. If not working, then add reset xform, and try to add the smooth modifier again.
So, I realize what this looks like... threw it together quickly so bear with me. The left sphere has had a proboolean operation applied to it. The right sphere is the same sphere just before the proboolean. I cannot for the life of me get the left sphere to adopt that smooth look again, Smoothing groups, UV's Normals,…