Aristotle's Ethics is indeed a foundational text. To simplify things greatly, there is basically only one alternative to it: Nietzsche. As Alasdair MacIntyre explains (the erstwhile Marxist, now Catholic, who helped revive virtue ethics with his book After Virtue), "the underlying structure of [Nietzsche's] argument is as follows: if there is nothing to morality but expressions of will, my morality can only be what my will creates. There can be no place for such fictions as natural rights, utility, the greatest happiness of the greatest number. I myself must now bring into existence 'new tables of what is good'" (AV 114).
Nietzsche is commonly misread as a nihilist, but nothing could be further from the truth. In fact, Nietzsche recognizes clearly that is precisely the installation of fictional moralities that is the source of nihilism, not the denial of those fictions. (This is also something that Heidegger sees clearly, e.g, in "The Letter on Humanism.")
At the end of the day, then, the question is this: Do you believe in some kind of "objective" morality that governs human life, gives meaning to our existence, and so forth? If so, then Aristotle's Ethics is by far the most cogent articulation of that view. However, if you believe that morality is just conventional, historically contingent, and a product of our "wills," then Nietzsche helps us see that clearest. To admit the latter view is not to succumb to nihilism; it is rather to free us to truly pursue the activities of greatness.
Ultimately, MacIntyre (inter alia) thinks that we have to choose. For an example of someone who, by contrast, tries to reconcile Aristotle and Nieztsche, see Hannah Arendt.
From an evolutionary perspective there are some objective morals, the most obvious being incest (simple genetics) and cold-blooded murder (mix of genetics and whatever dynamics give rise to human altruism, which is at the root of our specie's survival fitness).
Unfortunately, the universe defies simple, categorical distinctions. Kant's categorical imperative superficially comes closest to capturing the above examples, but not really, because Aristotle, Kant, and Nietzsche, all seem to side-step the question of free will, at least as it relates to the meaning of morality. Free will itself of course also defies simple distinctions. The problem in all these explorations of morality is that the number of implied assumptions is enormous, and it's the character of those assumptions which matters far more than the effectively trite observations about human behavior these philosophers often make.
Although viable offspring and stable communities are pretty natural choices for moral goods, a preference for the long term over the short term that predicates them is still a subjective decision.
It depends on your definition of objective, which is part of the point. What it means to be "human" will color everybody's preferences. How many outliers does it take for a preference to become subjective rather than objective? The nature of the question, more than the question itself, will determine whether something is "subjective" or "objective".
Are there objective moralities? Yes, if you qualify what objective means--e.g., approximately universally manifest preferences among humans. The particular morals, or at least the simplest aspects[1], will then tend to fall naturally from that.
But if our benchmark of objectivity is something completely abstract, then objectivity is unlikely to exist. Pure math allows us to create infinite universes with consistent rules, yet only one of those universes can exist in any physical sense. As long as you can pick from those non-existent realities (which is pretty much what philosophers do), then you can always rebut any claim of universality, objectivity, etc; or even, conversely, assert objectivity of a finely detailed morality by simply predicating a claim on your universe of choice (see, e.g., Social Darwinism).
[1] We don't have a good track record of fully comprehending biological determinants, especially as applied to human behavior. The interplay of culture and biology is extremely complex, and we suck at even identifying which is which, let alone inferring anything complex from the distinction.
Another way I like to phrase this thought (without getting into the details about whether Aristotle and Nietzsche agree or disagree), is that morality is a system of rules for making decisions. Turing machines and computation more generally allow for the implementation of arbitrary decision procedures. However, if you want that those decision procedures to be consistent, you need something else, namely a set of axioms. Goedel, Turing, Church, etc. have proved (more or less) that there is no set of axioms that gives universally true answers for all decisions, so there can be no provably objective system of morality. Thus, we must choose our axioms, if we do not, we usually choose implicitly (which I think is related to Nietzsche's abhorrence of slave morality). Aristotle represents a set of axioms that are practically applicable to many human relations, representing a pretty good default, if you have to choose one. Nietzsche says, (to use the words of another) 'choose again.'
I'm clearly not as deep as you in the reading of Aristotle (though I did read Nietzsche's BGE a long time ago). However, I'd point out the distinction from an ethics course I took between 'descriptive' ethics and 'normative' ethics. Both can coexist and they serve useful purposes.
The ethics of a group is the rule set agreed to by the group, including how to deal with deviations that naturally arise. This is more of a descriptive, evolutionary phenomenon. Normative ethics is more a proposal of an ideal or future ruleset, which needs to both appeal to those with the power to follow and enforce the rules, and to also ensure the preservation and stability of the rules and the people who follow them.
Nietzsche is commonly misread as a nihilist, but nothing could be further from the truth. In fact, Nietzsche recognizes clearly that is precisely the installation of fictional moralities that is the source of nihilism, not the denial of those fictions. (This is also something that Heidegger sees clearly, e.g, in "The Letter on Humanism.")
At the end of the day, then, the question is this: Do you believe in some kind of "objective" morality that governs human life, gives meaning to our existence, and so forth? If so, then Aristotle's Ethics is by far the most cogent articulation of that view. However, if you believe that morality is just conventional, historically contingent, and a product of our "wills," then Nietzsche helps us see that clearest. To admit the latter view is not to succumb to nihilism; it is rather to free us to truly pursue the activities of greatness.
Ultimately, MacIntyre (inter alia) thinks that we have to choose. For an example of someone who, by contrast, tries to reconcile Aristotle and Nieztsche, see Hannah Arendt.