It depends a lot on all sorts of factors like whether it's a comic or a novel, what genre you're in, whether you have an existing fanbase, whether you have friends with visibility to give you a shout-out, how and where you're promoting...
I can't remember how long 25 took me, but I reached 100 in just under 3 months. That's for a comic made by somebody with a modest existing fanbase and a history of professional work, but at the time I was in the Action genre, which isn't one of the easier ones. Basically, there's no point comparing, just focus on making entertaining and engaging readers. and building an audience as best you can.