No, sorry, but you probably aren't. Zynga isn't changing the world and neither are 99.9% of the startups coming out of SV.
The over-working culture is exactly that - a culture. It has nothing to do with actual reality, and everything to do with perceived reality. Great, long-term companies aren't built by entrepreneurs who sleep 2 hours a night.
P.S.: not getting enough sleep decreases productivity. The 37Signals guys have covered this a few hundred times at this point. I also seem to recall Richard Branson saying that he "needs his 8 hours."