The fabled “First Mover Advantage”. The thing we all clamor for, the stuff legends are made of and your worst nightmare if you’re late to the party.
Seldom does it really matter. History is full of companies which were not the first and still became the dominant force in their markets. As long as a market is not matured you are much better off focusing on your product and customers than worry about others.
Alando.de, the German auction site which later was acquired by eBay and became eBay.de was the 7th (!) auction site to launch in Germany in the mid-90s. Instagram was way behind the curve of Hipstamatic when they launched their photo service. Microsoft was years behind Apple in graphical user interfaces and still owns the market. Lotus 1–2–3 was lightyears ahead of Excel. Neither Friendster nor MySpace dominate social.
Focus on your product, your customers and your company. Not on the competition.