It'd be interesting to follow up each of these entries with what actually superceded the original in terms of market share.

"Original"/OSS/Current:

Office/OpenOffice/Google Docs

WinZip/7-zip/Whatever archive utility is bundled with your OS

Windows Media Player/VLC/Online Streaming

Netscape/Firefox/Chrome

In all but a few of the other cases (e.g. OBS), the original hasn't lost an ounce of market share to the "alternative".

I guess what I'm saying is the data seems to show that the threat to paid software isn't OSS alternatives, it's commercial competition.