At the individual level of course there is a huge genetic component to intelligence. Even with the perfect environment and all the money in the world you might just be a dummy.

But I'm not sure how you square the argument that intelligence is mostly genetic with population-level shifts in intelligence such as that of the Jewish-Americans that someone else brought up in this thread. The only thing I could see is those populations begin selecting for intelligence with regard to reproduction, but a couple hundred years is an extremely short period of time for something like that to happen at the population level if it's mostly genetic.