Adam is the key because he is the progenitor.
We know that they either get their powers naturally or through the syringe. The syringe had a version of the serum. The power they manifest is directly related to their personalities.
I suspect the natural powers are descendants of Adam.
The others get their powers from the formula.
To date Peter and Sylar have shown the greatest aptitude for powers. I thought the last episode was interesting not for Peter or the others, but for Matt. Previously he only had the power to read minds like his father. However in this episode with help he used powers previously that only Simon had used, and Peter used after getting from Simon, and Sylar used after taking it from Simon. The confrontation in the future between Peter and Nate was interesting too because it seemed there was interference like there is when Peter tries to read Matt's mind.
The manifestation of the power is personality.
Nikki felt threatened, she felt weak so she was given super strength
Her Triplet was we have to admit a cold bitch and has the power of cryokinesis.
Nathan felt trapped by his life, so he gained freedom in flight
Gabriel had a hungering desire to be more than he was, in some ways he is like Anakin Skywalker, he hungered for more than he was and lost all he was.
Claire like most youth thought she was indestructible, and thus she became indestructible.
Hiro felt trapped by his life too, he felt he was not living up to his father's expectations. He gained control of time.
Daphne seems to be a free spirit, wanting to go where she wants when she wants, she got super speed.
DJ wanted to be free and learned to phase through walls.
Micah like most kids was a bit to much into his electronic games and such and through the extension of them learned to control machines.
So on.
(Keep in mind Adam is indestructible too, and possibly to a higher degree than Claire)