People use a lot of different definitions of "indie" these days.  A lot of people use a definition that includes any game where the creator is not beholden to a publisher.

Personally, I like to draw a distinction between "indie" and "hobbyist".  Under my personal definitions an "indie" is not beholden to a publisher, or at least has full creative control over their project and provides (or crowd sources) their own resources for development. But they're also a business-like professional. They likely have a proper registered business, and they do things like market research, testing, marketing, etc.  They likely pay employees or contractors rather than relying on free help or revenue share.  A "hobbyist" is people who are creating a game in their spare time with minimal resources and likely isn't doing all (or many of) the business-like activities listed above. 

The "shareware" terminology is a bit dated, but basically the distinction from Shareware Amateurs vs. Shareware Professionals.

So, under these definitions, hobbyists are often the people who don't complete their projects.  When they do complete them they are frequently lower quality projects that don't get a lot of plays or are not commercially successful.  Sometimes they're not even aiming for commercial success - and that's absolutely fine!  All that business-like stuff isn't for everyone.  "Art games", "experimental games", "trash games", game jam entries, and all the other wonderful things that hobbyists produce have their own value.

Using my definition of indie where development is professional and business-like activities are carried out, I would say most projects are at least completed, and a reasonable portion at least manage to break even or make a little profit.  Sustainable success (which I think is what you're talking about) is, however, more rare.  Huge break-out successes like Minecraft, Angry Birds, etc. are statistical outliers.

I don't have the link handy right now, but there's a video of a presentation where someone looks at the % of Steam releases that earn over certain thresholds that may be illuminating.