No they're not. They're just as strong as the average vampire but they have more expericence when it comes to fighting as well as the volturi guard. Infact, vampires are strongest in the first two years of the vampire live due to the excess of human blood still in their systems. Their strength fade eventually.
EDIT: Aro, Marcus and Caius are actually the weakest vampires because of their age (hence their bodyguards), but they aren't as weak as you think - they can still kill other vampires that are younger then them with ease. Vampire's are at their strongest in their first year of vampirism, because of the human blood still in their systems (as above), but the strength fades because the blood does not stay there for all their existence. --188.8.131.52 11:59, July 4, 2010 (UTC)