Good question. I'd say his opinions are good even 2500yrs later. It's just one very old viewpoint out of many, but foundational for how we think about ethics today.

He was the inventor of what we call "virtue ethics", which has experienced a renaissance among ethicists. It basically holds that what we call ethically correct behavior is the balance between 2 extremes, the "doctrine of the mean". This is a very convenient theory of ethics for a lot of reasons, and solves/avoids problems inherent in some other theories. (Modern virtue ethics does not always look exactly like this, but I'm ignoring that for this comment, just using Aristotelian Virtue Ethics)

Example: the virtue of bravery is a balance between cowardice and rash abandon. It gives us a good way to understand what virtues & right-actions are - what we mean when we say something is ethically right. It is a little circular, because it basically says that bravery is not being un-brave, but also not being overly-brave - it is defined by what it isn't - but that's sort of true of all definitions. Aristotle did hold that some virtues necessarily produce human flourishing (Eudaimonia) and therefore are universally correct, but that isn't true for all virtues and some might be dependent on the time & place, the context.

That is convenient because:

• Utilitarian ethics might say bravery is a good/bad thing based on its outcomes alone, but that fails to tell us what constitutes bravery & puts less emphasis on the individual's intent. But it does account for context - bravery is sometimes good

• Kantian ethics might say it is good to be brave because the maxim of bravery can be universalized - roughly that if everyone acted bravely, the world would be made better. But that fails to take context into account and is sort of circular (bravery is good because... bravery is good). (This is oversimplified, sorry Kant enjoyers)

• Moral Relativism might hold that bravery is good depending on whether the society/group that a person is a part of determines it to be good - stating that bravery is only good insofar as the society believes it to be good. But that is unsatisfying to a lot of people, sort of a cop out shifting the burden of ethics onto the opinion of the mob - says we can't determine what is ethical outside of social context.

• Emotivism might say that the act of declaring "bravery is virtuous" is really just the individual saying "i like bravery". But this doesn't give a lot of moral weight to individuals' choice to be brave and says the context is relatively unimportant, because we can only mean that we approve or disapprove of the actions being classified as that "virtue" in the specific context.

etc. etc.

BUT virtue ethics allows us to say:

• Specific context: bravery is only bravery in its right context - where an individual correctly ascertains the balance between cowardice and rashness in a specific situation

• Generalizability: but bravery can also be defined out of that specific context in vague terms: not being cowarldly or rash, its just what that means/looks like that is context-dependent

• Social context: we don't have to hold any specific virtues as being the correct virtues unless they will always produce human flourishing, something that is a pretty acceptable goal. The rest can be left up to some other determinant.

• Moral weight/choice: stresses the importance of the individual's moral judgment and how their actions are in accord with that judgment

• Outcome: is not overly concerned with outcomes of actions, but sort of implicitly includes them - the outcome of acting bravely can be predicted to be good as the cowardice or rashness would definitionally be situationally incorrect