I've just put together our Top Ten Graphic Novel Recommendations as determined by our customers through twitter and facebook. I asked specifically for books that you'd recommend to somebody who'd never read a graphic novel before...
1. Batman Year One 2. Y The Last Man 3. Kingdom Come 4. Preacher: Gone to Texas 5. Transmetropolitan: Back on the Street 6. Wolverine: Old Man Logan 7. Criminal: Coward 8. Scott Pilgrim's Precious Little Life 9. Marvel Comics Civil War 10. Watchmen
If they have never read a graphic befor are you sure watchmen would be a recomendation (I am asumong that this person is new to comics all together). I am not spouting my usual watchmen hateing just saying is it a good choice for a new reader. Particularly as it just jumps into the pirate stuff.
I guess people recommend Watchmen as it's perceived to be the best, and able to show what comics can achieve without breaking too many conventions and being too crazy and offputting.