Wow, that's quite a question! :) I think that the only question even more complicated would have been: "What's the correct ethical theory?".
I'd say it largely depends on the meta-ethical assumptions you use. It might also depend on the understanding of rationality. Say, if we understand reason as fundamentally instrumental, then we likely won't be trying to ground morality in reason itself.
Anyway, why do we talk about ethics at all?! Well, because there are "phenomena" of people finding some "things"(acts, dispositions, etc.) to be good/right or bad/wrong in a special(!) sense of those words. Moreover, these are not just observational characteristics of "things", like "hey, look - that tree is green", these moral characteristics have some motivational power. This motivational power is quite distinct from the egoistic motivation - it does have "a sense of ought".
So, any meta-ethical theory should try to explain why there are such characteristics, and what is their nature. Whether we find them in the world, in reason, in upbringing, whether they are just expressions of emotions, likes/dislikes, etc. Now, the ethical system should (unsurprisingly) try to find a rule, a system, behind those moral phenomena in our lives. Whether we find something moral if it maximises happiness, or maybe morality is just a set of rules like "though shall not kill", or there is something else to it. But in any case, it should deal with the moral phenomena we encounter, hence the importance of intuitions and hypothetical examples. Every deviation from intuitions should be explained by the meta-ethical position, i.e. how can something be moral according to the ethical system and yet we do not find it to be so. Or conflicts of intuitions should also be explained by the meta-ethics.
That's, of course, my opinion on the matter! And it's a quick informal answer too... :)