Gatsby - American Dream
Many critics have said this is a novel about the American Dream. Specifically, that this is a novel that illustrates the hollowness of that dream, the impossibility of it in the 20th century world. The very end of the novel addresses this. Reread the novel’s final page. What was the dream “that flowered once for Dutch sailors’ eyes”? What has it become in the world of this novel? Consider what Fitzgerald writes on page 169 in the next to last paragraph. Consider also any contrasts between the world Fitzgerald describes on the novel’s last page and the world symbolized in the valley of the ashes.
The American Dream was is and always will be about hope. Watch Americans in trouble, they have belief in a hope or promise of a new future.
The 20s was all about materialism. People got wrapped up in their entertainments and parties. While that's all good and fine, it has a limit, or limits. That material lifestyle doesn't fulfill. When all one works for is one's self, one feels less fulfilled than when one gives to others. This is where Gatsby lived. Gatsby met his own needs.
The folks that first came here (Dutch sailors included) save this place as an adventure, a place for a fresh start, a place filled with new hope.
By the 20s, that had been overfulfilled and people began to move backwards.
The sentence you note is a beautiful one to pick apart for meanings. It is full of ideas about what we hope for but cannot grasp.
Concerning your question about The Great Gatsby, the final paragraphs of the novel are not primarily about the American dream. They're primarily about Gatsby's dream, and that dream consisted of recapturing his past relationship with Daisy.
Nick ends the novel talking about recapturing the past, like Gatsby tried to do. He, in fact, is on his way back to the Midwest, in a sense at least, to do just that.
Nick metaphorically compares the wonder that must have been felt by Dutch sailors when they first saw this new continent, with Gatsby's wonder when he first saw Daisy's house from across the water. But notice the wonder the Dutch sailors felt led to an "aesthetic contemplation," not to thinking about money, and Gatsby already had money. He wasn't looking for the American Dream when he first gazed at Daisy's home--he already had it--he was looking to recapture his relationship with Daisy--he was looking for love.
One might be able to argue that when Nick refers to the "orgastic future" he is talking about the American dream, but it certainly is not the primary focus of Nick's conclusion.