I'd recommend more than two hours - it is possible to do it in that time, but would leave absolutely no room for error.

Flying on EK203 back in April, the flight was an hour late departing, and it looked like JFK immigration was having a bad day, judging by the number of people being taken to "the room".

As a result I was still in the immigration queue when my connecting flight - not my choice of booking sadly - took off (which resulted in one of the least pleasant travelling experiences of my life thus far - yay).

My $0.02: aim for more time...