Sure the title may be jumping the gun a bit, but you're severely overhyping SF and underestimating NYC with your comment. The fact that Fog Creek and Reddit (moved to SF) were the companies that came to mind shows that you don't know the NYC tech landscape well.
On top of the condensed list below NYC has Columbia, NYU, and Cornell Tech in terms of talent pool, and one of the most extensive transit systems in the world.
1. Bloomberg 2. Oath (AOL + Yahoo) 3. Blue Apron 4. Buzzfeed 5. Tumblr 6. Etsy 7. AppNexus 8. Flatiron Health 9. Oscar Health 10. Shutterstock 11. Squarespace 12. IAC (Tinder, Match.com, OKCupid, etc) 13. Zocdoc 14. Compass 15. Casper 16. MongoDB 17. Warby Parker 18. Vimeo 19. Betterment 20. Classpass 21. DigitalOcean 22. Foursquare 23. Fanduel 24. Stackoverflow 25. SeatGeek 26. Birchbox
etc.