Yes, you can certainly lathe a 100-sided N-Gon into a sphere shape, though you will end up with a doubling of the mesh since the object would actually be a torus with a diameter of zero. A simpler way is to start with the basic sphere primitive and subdivide it, either by converting to a subdivision object (Build > Convert to Subdivided) or converting it to a mesh (Build > Convert to Mesh) and using the Build > Smooth Object command with a tension of 0. In the latter case you can smooth as many times as you like, doubling the number of lat/long lines each time, and the result is an exportable mesh.
Subdivision objects use an algorithm to determine subdivisions between the basic mesh so an exported version of the object may only include the original low-res mesh, but this can be resolved using Build > Convert to Mesh. Subdivision objects are excellent for 'organic' models that will be morph-animated, since you only need to animate the coarse mesh while allowing the subdivision algorithm to smooth everything out.
One thing to note: due to its topology the sphere primitive may look a bit pinched at the 'poles' when subdivided. Subdividing the dodecahedron or icosahedron primitive results in something more like a geodesic object without polar distortions and approaches a spherical shape with a couple of subdivision stages.
EDIT: I momentarily forgot that the sphere object can be converted from lon/lat topology to geodesic by double-clicking to open the object dialog, and the geodesic divisions can be defined (max 6). While not strictly a true geodesic it may subdivide more smoothly than the lon/lat topology.
