Different publishers clearly have different approaches to marketing; you just have to compare Square to THQ to see that. Who does the marketing is totally irrelevant to how successful it is (beyond the idea that farming it without giving a shit probably gets poor results).
Marketing firms have different ideas as well how to advertise products, nothing is done in a vacuum, when you sit down with a firm and describe your product (A standard step) in an ideal world you should be telling them what your product's high points are, which they should then turn into selling points. Taking those selling points then should (Again ideal world) figure out how best to sell it to the product. For example a billboard campaign on highways makes no godamn sense to promote a song or new artists. But a subway add with a smart phone code built in so your bored and captive audience can hear the song makes a whole lot more sense and when you price things out the subway add will be cheaper and up faster than the billboard campaign. Random marketing example I know but I'm building to a point here stick with me.
Marketing firms just like any other business learn how to do something well or deliberately specialize in a thing then do it over and over again, thus THQ's advertising is because those they work with try to sell everything like it's a WWE game or everything like it's their latest Disney title and all of their products get funneled into those two framing devices.
Valve is a good example though; they have extensive, high quality marketing that focuses on anything except gameplay. Their approach is probably the extreme in the 'sizzle not steak' direction, and it clearly works for them.
Again video games have to steal ideas from Toy Marketing because some percentage (I've heard everything from a third to two thirds) of video game sales are bought by people who won't be using the product but are buying it for others.