I know the "what you refer to as Linux is, in fact, GNU/Linux" thing has become a sort of tongue-in-cheek meme, but it actually applies here: crediting Linus Torvalds alone for the success of Linux ignores crucial contributions from RMS, Ken Thompson, Dennis Ritchie and probably dozens or hundreds of others.

Ruby on Rails? Are we talking about the Ruby part (Matz) or the Rails part (DHH)?

Dropbox was founded by Drew Houston and Arash Ferdowsi. The initial Gmail development team had multiple people plus the infrastructure and resources of Google. I'm not sure why people love the lone genius story so much, but it's definitely the exception and not the rule.