Well I guess depends on various definitions...and maybe who gets to write the history books.
For a few years (guessing about 200 somewhere in the window of post apostle, pre-nicea) Christianity was considered a cult in Rome and other places. I say Rome primarily because at that period of time Rome was the center of the 'civilized' world.
Islam is considered a religion and not a cult. And yet everything we think of instinctively when we think of the word ‘cult’ is embodied in Islam, times a million.
So in a sense, there is no objective criteria beyond number of adherents and time on earth. Once you’re established, you’re a religion, no matter how sick and evil your practices are.