The prerequisites of course being in the right place at the right time, with the right people and a little luck on your side as well.
So many people are remembered just because there were first at something by like a week, and the dozen others who also thought of it elsewhere but were a bit late or didn't publicize as well are forgotten forever.
Very rarely being first counts imo. If you are building something novel in parallel there is a good chance you will have enough of difference.
Examples: other search engines, social networks, 3d games still exist. For many folks a different graphic on your homepage can be differentiator enough. (If you ever wonder why A/B, SEO, copywriting, design/ux is important)
id wasn't first in a lot of things. They were essentially porting existing graphics technology to the PC. They succeeded because other programmers turned their noses up at the "underpowered" PC in favour of systems with "better" hardware. Carmack certainly did a lot of work and devised some ingenious ways of getting the most out of PCs but he was adapting things more than pioneering them.
