There are many ways to tackle this I believe and you will have to choose based on your content and your audience. There have been studies on where people look first and what different audiences expect. Which is to me one of the most important factors. Of course, functionality plays into it as well. Will there be very deep submenues? Then it is often favored to have a left-aligned menue that expands and collapses. Will there only be three major pages? Then maybe a horizontal menue will be better on presenting them at one glance. But again, it depends on many factors, so just take those as examples.
Ok, let's start with your left-top statement. Yes it is most prominent spot on a website. And because of that, it often features the logo or the name (answering the "where am I?" question). People start expecting that. So if you break this rule, make it obvious to your audience. The logo on the top left corner also often (and should, really) features the link to the main page (answering the "how do I get out of here?" question). But since you now have a navigation point, you could work from there, depending on your content, amount of content and target audience.
And that is just an example of how to target this and not a solid rule.
So, instead of asking where to put the menue, you should analyze what you are trying to achieve and for whom. And then take it from there.
(hope that wasn't too meta)