Increasingly, the web is becoming an entertainment and commercial medium.
In which case my statement stands -- since that entertainment (media) is CONTENT.
You say "content first" and for some reason people seem to think you only mean text -- if you have a content image or movie you say that element's filename and alt text (or whatever is appropriate to the media type) in your starting flat text file.
If it's what the user is there to get, it's content. Therein that's the ONLY part of the site that really matters. Doesn't matter if that content is text, a movie, a sound file, or an image -- that's what people are going to the site FOR. Everything else is window dressing.
... and I'm not saying you can't make it attractive, but that should be the last step, like siding and paint on a house. There's no sense in trying to paint a house that the architect hasn't even laid out the frame for yet. It's akin to hiring an "artist" to design a skyscraper who knows nothing about architecture -- some thirteen years later and you're still pushing back the opening date after billions of dollars of cost overruns. Just ask New York City about that one.
... and if I'm pushing these views a bit vehemently, it's because I'm sick of watching people being led down the garden path to failure. Most of the 'artists' out there sleazing out PSD's simply don't know enough about HTML, CSS, emissive colourspace or accessibility to be 'designing' a blasted thing for anyone, which is why at the scam artist whorehouses like ThemeForest and TemplateMonster all you are going to find is a bunch of nube-predating bull none of which has any business being deployed on a real website.
Lemme put it another way -- ever wonder why Vimeo, or worse smaller sites have NO CHANCE of ever making a real dent in Youtube's traffic? How about how most official game websites are useless messes nobody goes to, allowing fan sites to blow them out of the water? Rockstar's official game sites vs. sites like GTAGarage (and it's dozen sister sites like gtav.net) comes to mind.
You don't have to look very deep to figure it out...
Oh, and yes, GTAV.net is a media heavy design heavy site with a lot of accessibility failings -- it's also content driven and a dozen times more useful than the steaming pile of artsy-fartsy crap Rockstar has because of it's clean navigation, layout and ability to actually SHOCK get at the content. I could rip it a new backside for the endless pointless DIV for nothing and outdated site building methodologies, but at least the content is there in a useful manner... there's no reason what a site like that has couldn't have been built the way I'm saying, faster and in less code for less effort, while being more accessible... but you go to http://www.rockstargames.com/V/ and all you end up with is the overwhelming urge to punch someone in the face from the splash screen/age verification ALONE. You get inside the site, it's such a slow loading bloated inaccessible mess of "I can haz intarnets" I would be genuinely shocked to find anyone who could call that site useful, much less worth visiting. It REEKS of letting some artists and scripttards just walk through a pile and track it all over the web!
There's a reason the 'design first' and "accessibility, what's that" approach to development is restricted to certain types of sites; most of which are miserable failures -- Brick and Mortars for whom a web-presence is an afterthought, small personal sites where someone got duped into paying their way into thinking they have a website, Official gaming sites where they are so obsessed with "wow" they don't care if anyone actually visits the pages, and of course, the personal sites of such designers themselves.
... and there's a reason you'd be hard pressed to find a major successful website using any of that crap. Unless you have a magical cult of followers like Apple or Ikea, flash over substance thinking is the road to failure.
We can't all have followers who go "I'll buy anything shiny with an Apple logo on it"