The fact is that there is only one real best chapter, Imperial Fists! mouhahaha
In all modesty of course, xD

Yeah, killing Imperials for doing their job is the mark of a good Chapter.

Black Dragons 'BONE AND FIRE '

they stand 1m higher then the average marine and have awesome bone like blades coming out of there wrists and foreheads

You are overreacting!They were not trying to annihilate the word...just to resettle its population and sterilize it.They have fought against a Daemonic Primarch and were subjected to a lot of Chaos taint!

Do not resist they Eye that sleepeth not!
Praise the Omnissiah!

Hey, when the emperor created you to be a hammer, is it your fault that everyone looks like nails?

Asking what the best chapter is, is like asking what the best colour is.

Bloodred!
Well, the "best" chapter in terms of most powerfull would be the the Deathwatch or the Greyknights (Wardism and best equiptment)
In terms of flavour, well there we can agree with Blazebro

So: I go with the Alfalegion!

That's why the Rainbow Warriors win: they wear all of them.

If you go with most powerful, wouldn't you have to include Black Templars as well, out of sheer force of numbers, piled on to the fact that they're regularly equipped Space Marines (with a penchant for melee....).

Brothers we have A traitor among us.