With The Great Gatsby, is Fitzgerald writing a love story that embraces American ideals, or a satire that comments on American ideals?

I think that Fitzgerald's feelings about the American ideals in the 1920s were decidedly negative and I highly doubt that The Great Gatsby celebrates those ideals in any way. Reading the book for the first time is an overwhelming experience, and the dazzling images of grandeur that the book invokes at nearly every turn can be blinding and alluring. Initially, I, too, wondered if this story embraces the high and exciting lifestyle of the wealthy in those days, which is part of what makes this book so impressive. The Great Gatsby perfectly describes the romping and glimmering world of the rich in the 1920s and even lets the audience grow fond of it before declaring in no uncertain terms that all this money and brilliance masks a brutal and harsh reality.

Fitzgerald wrote a wonderful social commentary about the age he was living in, yet it doesn't entirely qualify as a satire. While the story clearly possesses some satirical elements, perhaps most clearly present in the character of Tom Buchanan, it lacks the immense and comical irony that is so often in other famous works of satire, such as The Importance of Being Earnest and An Ideal Husband by Oscar Wilde. 

“In matters of grave importance, style, not sincerity, is the vital thing.” 

“I never change, except in my affections.” 

Both these quotes from the third act of The Importance of Being Earnest embody the dual function of a satire: to be humorous while simultaneously surprisingly accurate about the true nature of some aspect of society. To be totally fair, some of Tom Buchanan's lines are funny to a certain degree because of their utter stupidity. 

“'This idea is that we’re Nordics. I am, and you are, and you are, and ——' After an infinitesimal hesitation he included Daisy with a slight nod, and she winked at me again. '— And we’ve produced all the things that go to make civilization — oh, science and art, and all that. Do you see?'”

This is a quote from chapter 1 of The Great Gatsby and it is of Tom explaining why, for some faux scientific reason, the "white race" is superior. In the very next paragraph Nick remarks to himself that there was something pathetic about it all. Indeed, Tom's various racist and sexist lines are moderately funny, mostly because of their extreme and idiotic absurdity. Even Daisy is shown to find his ridiculous remarks mildly entertaining. Yet, more than anything, these lines are understandably offensive and unsettling, especially when one considers that Nick is "friends" with this horrible man. 

Although some might disagree, this story is far too grim and hopeless to qualify as a true satire. The social commentary inherent in The Great Gatsby is powerful and immensely striking, yet for vastly different reasons than that of social commentaries like The Importance of Being Earnest and An Ideal Husband. Both of these stories have happy endings and are comedies by nature. The Great Gatsby ends with two deaths and with Nick Carraway leaving West Egg. The story, despite some of its humorous dialogue, is ultimately nearer to a great tragedy than to a comedy.