I never was a JW but have read a lot of their history on this and other sites. There are several definitions of 'cult' and it seems to be a fine line between 'wacky religions' and 'cults'.
My gut reaction is that a 'cult' imposes an inordinate degree of control over its adherents, with consequences and sanctions for those who fail to comply. JWs certainly fits that.
My first reaction to the OP's question was that in its early days, Russell's 'break away' or 'spin off' from the Millerites et al was just a 'wacky religion' started at a time and place which seemed to foster so many 'wacky religions' and that it was under Rutherford that the 'control' issue became major (possibly to keep 'his' JWs separate from the original mainstream IBSA).
Now, I'm not so sure. The more I read of Russell and the machinations of his early collaborators the more I come to the view that this was a 'cult' from the beginning.
BTW, I find it interesting how time and history tends to lend credence and respectability to wacky religions. Joseph Smith's new religion was obviously nutty (at best), Russell's pyramidology survived and flourished, and to be honest Saul/Paul's new religion based on visions is pretty wacky on any objective analysis. But they have survived, and as time and distance cloud their origins they gain (in some quarters at least) a degree of respectability. With the advent of the internet and the huge availability of information to all who wish to find it, I don't think it would be so easy to start a new wacky religion/cult now. (Edited to add: unless of course, the cult/religion proscribed independent research - ring any bells?)