It all depends on what one decides to be a definition of a "success story." For some entrepreneurs, it might be getting acqui-hired, for some -- a $10M exit, for some -- a $200M exit, and for others -- an IPO.

Based on the numbers I have anecdotally heard in conversations over the last decade or so, VCs fund about 1 in 350 ventures they see, and of all of these funded ventures, only about 1 in 10 become really successful (i.e. have a big exit or a successful IPO.) So you are looking at a 1 in 3500 chance of eventual venture success among all of the companies that try to get VC funding. (To put this number in perspective, US VCs invest in about 3000-3500 companies every year.)

In addition, there might be a few others (say, maybe another 1-2 in every 10 companies that get VC investments) that get "decent" exits along the way, and hence could be categorized as somewhat successful depending on, again, how one chooses to define what qualifies as a "success story."

Finally, there might also be companies that may never need or get around to seeking VC funding.

One can, of course, find holes in the simplifying assumptions I have made here, but it doesn't really matter if that number instead is 1 in 1000 or 1 in 10000. The basic point being made here is just that the odds are heavily stacked against new ventures being successful. But that's also one of the distinguishing characteristics of entrepreneurs -- to go ahead and try to bring their idea to life despite the heavy odds.

Sources of some of the numbers:
http://www.nvca.org/
http://en.wikipedia.org/wiki/Ven...
https://www.pwcmoneytree.com/MTP...
http://paulgraham.com/future.html

Here are others' calculations of the odds that lead to a similar conclusion:

1.Dear Entrepreneurs: Here's How Bad Your Odds Of Success Are
http://www.businessinsider.com/startup-odds-of-success-2013-5

2.Why 99.997% Of Entrepreneurs May Want To Postpone Or Avoid VC -- Even If You Can Get It
http://www.forbes.com/sites/dileeprao/2013/07/29/why-99-997-of-entrepreneurs-may-want-to-postpone-or-avoid-vc-even-if-you-can-get-it/