I bet that if some of them wanted to they could choose to be Good or bad.
id say bad cuz they want power
they enforce law.........but sometimes they are cruel... but they have to be to not be overruled... so overall they are okay!
Well I'm not saying they are angels, but they're not really evil, either.
Sure Jane and Caius are a bit -Ok, VERY- sadistic, but imagine the world without the Volturi: CHAOS! Everywhere vampires killing people and well just simply chaos describe it.
About the Cullens situation, well, they are kind of a threat to the Volturi... and they are vampires for the God's sake! not fluffy Teddy bears!
The Volturi are vampires real, are not that bad comply only contraryto their nature Cullen!