Daisy's ability to love without conditions or compromise is what has been destroyed by Tom's "hard malice".
In agreement with the above posts, I'd say that it's true that Gatsby's dream was not for "the real Daisy" but for Daisy as she once was. This is an impossible and irrational dream. The reason it remained "fresh" is because it was almost literally an image of freshness, of youth, of a night when the world was young.
However, dealing with the specific language of the question, I'd suggest that Daisy is the freshest and best thing about Gatsby's dream and she has been damaged by her relationship with Tom.
The freshest part of Jay Gatsby's dream is that throughout the narrative, he remains idealistic. At the end of the novel, Tom reflects,
Gatsby believed in the green light, the orgastic furture that year by year recedes before us....
Because of his genuiness and idealism, Tom tells Gatsby shortly before his death,
They're a rotten crowd....You're worth the whole damn bunch put together.
Gatsby has always looked for the green light at the end of Daisy's pier, but in reality he is the only light in the amoral world of decadence in which he strives.
The freshest part of Gatsby's dream in my opinion is that he believes you can still "go back again". It is such a child-like idea that one can turn back time and recapture a portion of your youth when you were happy and you had the love of your life.
Most adults (including Tom), have become jaded and place their happiness in the firm grasp of money, material posessions, and status. When Tom's malice (desire to "win" by stealing Daisy back from Jay) leads him to tell Myrtle's husband that Gatsby was the one that killed Myrtle...he was knowingly sending Gatsby to his death (thereby killing the innocense of his dream), just so he could "win".
I agree with #6. I think it is clear that above all, Gatsby's dream relates to his desire to completely transform himself and make himself into a completely new person, removed from his humble origins and becoming Jay Gatsby. It is Tom with his determination to discover the truth behind the figure that Jay Gatsby has become who punctures that dream and makes Gatsby realise that we are not able to transform ourselves and completely forget everything about our past in the way that we would often like.
Gatsby's dreams are WAY bigger than to be loved -- by Daisy or by anyone else for that matter. The power of the novel comes from the last chapter when Gatsby's father comes for the funeral and brings with him Gatsby's childhood list of "personal self-improvement" goals. He clearly wanted more from his life at a very early age and took the necessary steps to achieve that. Remember that in order to attend college at St. Olaf he had to work, but the work he found demeaning and he left because the school "did not hear the beating drum of his destiny." He joins up with Dan in order to make a living, but also to learn how to get rich and live like a rich man would.
Gatsby wants to be loved by everyone. He does want to earn Daisy, but his bigger object is to be the focus of attention and have a reputation as a pillar of society. He wants to be wealthy and important, and everyone's friend.------------?
I completely agree with the view-point of the third poster. I believe that his desire to be loved is the main desirable dream. Outside of this, his behavior and his quest for the love of a woman who is "unworthy" is not pure at all.
I don't think Gatsby's love for Daisy is that fresh and pure because she's so (as the previous post says) unworthy. I think that the freshest part of Gatsby's dream is his general desire to be loved at all. I think that you can argue behind his pursuit of Daisy is a desire to be found lovable. That sounds fresher and purer to me than wanting Daisy herself.
Gatsby has been working for the better part of his adult life for one thing--to be worthy of Daisy Buchanan's love. She is an unworthy object of his love, and we know he was involved in shady (illegal) business dealings in order to achieve his goal, but the goal and his motivation--his desire for Daisy--was pure. Tom's hard malice caused Gatsby's death because he told George Wilson it was Gatsby who killed Myrtle. This puts an end to his life as well as his dream of Daisy loving him--and only him.