The Vampire Diaries has more drama than action, unlike The Walking Dead. However, TWD quickly got repetitive and boring. The characters are simple unmemorable, as there has been no character development throughout the whole series. The writing and plot is also terrible.
Unfortunately most don't care about these technicalities, or don't understand them therefore as long as TWD has blood and action, they'll give it good ratings. I don't care much for TVD since it also have things that needs fixing, but I'd still say it's better than TWD.