An American version would be a bunch of super cuts of people talking about how boring the series is to their friends. First on the school playground, then on USEnet, then on AIM and GameFAQs, and finally on 4chan. Fade to black, "Dragon Quest. Yeah, we still make those."
I think it would be a few people mailing in a registration card to Nintendo Power and getting DQ1 in the mail, followed by a bunch of silence, followed by people buying DQ8 for the FFXII demo, followed by more silence.
The problem with DQ for most people (aside from your typical western/xbox game player who is averse to anything Japanese) is that those that may have been casual fans of the games in the past aren't aware of new ones. I remember at my first job, I became friends with someone who didn't play games AT ALL. But back in the day he loved 2 games - Punch Out and Dragon Warrior. He was shocked there were 8 (at the time) games in the series, in fact he didn't even know there was a sequel back when he was little and still played games.
My personal commercial would be - being 6 and renting Dragon Warrior from a mom-and-pop video store, struggling for an hour to get out of the throne room, fighting slimes and leveling up, renting 2 later and not liking it, waiting for what seemed like an eternity for 3 to come out, surprised that 4 came out pretty quickly after 3, beating it and letting my new friend (to this day my best friend who is also a big series fan) borrow it in exchange for BOF1, then silence for a while. Till I decided to import 5 and 6. More silence, then getting 7 and my friend's girlfriend saying to me "oh wow I didn't know they still made those games, I loved 4 when I was little!), then loving 8, then disappointed at 9 at both a gameplay and choice of platform perspective, then getting so pissed at how SE constantly mismanages the series, then starting a new job working with a bunch of Japanese people who like the series and telling them about the (imo shitty) localization changes we get.