Hmm, if I'd never been born...
Mankind would have achieved world peace by now*.
Hunger and poverty would have been conquered*.
The first interstellar faster-than-light expedition would have returned last week and announced that there's at least 50 different alien races all of whom want to meet us*.
Inane topics would receive short order on Sciforums.
Someone else would be living in the premises I currently occupy.
* PS, I don't feel in the slightest bit guilty for these. You guys just didn't put in the necessary effort.