I apologize if this violates blog policies, as far as I can tell it's within the boundaries set.
By necessity, science fiction changes form as technology, politics, understanding of the universe, etc. progress (or perhaps regress, depending on your thoughts on certain subjects). My issue with modern science fiction, therefore, is not in regards to the fact that it has changed form; it is, rather, the form it has chosen to assume.
In what I consider the best age of science fiction, the 1960s-80s, the common science fiction universe was a universe at war. The result of different cultures coming into contact with each other was what may well be expected: Some cases led to beneficial alliances, while others met with prominent clashes of culture, often resulting in war. As someone said (I would give credit, I simply cannot remember who it was), science fiction is a product of the culture that produces it. These universes are a direct result of the Cold War and the conflict of Communism versus Capitalism.
Clearly, that is not applicable in the modern era. Almost anyone below the age of 30 (myself included, admittedly) does not know what it is to have a clear and constant enemy. The wars of today are fought against insurgencies, except for the conflict with the Taliban government in Afghanistan in 2001-2002 and the war against Saddam Hussein's Iraqi government in 2003. Since those conflicts ended, we have lived with the fact that not all Afghans are bad, only some of them. We have no clear and present foe, as a result science fiction has turned to different issues.
Most modern science fiction that I have seen is what's called social sci-fi. It attempts to address issues the author finds in our society, which usually winds up making a political point. Now, this isn't necessariliy bad. Simply because I disagree with many of the points (most are politically liberal, I am conservative) does not completely generate my opinion. Rather, I miss the grandeur and the sheer cool of 20th century science fiction. While that seems shallow, I think all of us, as players of Halo, simply think it's cool when the 27km long ship materializes in Reach's sky, immediately opening up with its ventral turret and knocking a frigate out of the sky. That is why Halo is my favorite universe out of all of modern science fiction.
Besides, one can still explore morality on the battlefield.