To be clear, for every machine type, we are offering a HT per virtual CPU. So that means that an n1-standard-8 instance gets 4 physical cores and 8 hyperthreads. (We are also offering 3.75GB of RAM and ~440G of ephemeral disk per vCPU).
So I would say:
n1-standard-1: 1/2 physical core
n1-standard-2: 1 physical core
n1-standard-8: 4 physical cores