How do Plato and Aristotle define the good?

Both philosophers make the argument that "the good" is
something that must be pursued as part of one's nature as a human being.  At the same
time, both of them understand this pursuit as something that must take commitment and a
sense of courage in order to embrace and, eventually accomplish.  Yet, both thinkers
define "the good" in different ways.  For Aristotle, this is an internal quest. 
Aristotle believes that every human being has a "good" end within them and they must
recognizes this.  Ethical conduct comes out of this understanding.  It is here where
Aristotle defines this pursuit as the "golden mean" where individuals recognize good as
the balance between two ends.  For example, ambition is good, but too much can be bad. 
Ethical conduct for "the good life" is found by the individual in this moderation. 
Plato differs in his notion of "the good."  Plato defines "the good" as the embrace of
"the form," the ultimate good.  This is an external reality that Plato readily admits
not everyone can achieve.  The "form" is an ultimate good that defines "the good."  In
this, Plato's conception of the good is something that is divergent from
Aristotle's.