I found the Sam/Dean(/John) - Lucifer/Michael(/God) parallels interesting.

[SVfan26]

• Sam-Dean = Brothers / Lucifer-Michael = 'Brothers'
• John is S&Ds Father / God is L&Ms 'Father'
• S is the youngest sibling / L is the youngest 'sibling'
• D is the oldest son/ M is the oldest 'son'
• D was always the 'good' son or 'perfect soldier' / M has always been the 'good son' or 'perfect soldier'
• S was always the 'rebellious' son that disagreed with Js methods and actions / L was the 'rebellious son' that disagreed with G
• S wanted 'normal' and left his family to get it / L wanted to prove himself and left his 'family' to do so
• D always did what J told or wanted him to do / M did the same for G

Just thought that the parallels between the two sets of brothers(& fathers) seems to almost directly correlate with each other's past and present.

[stovers]

It is interesting. I think that why the Winchester family was chosen.

[papercrow27]

I had this same epiphany the other day, but then I kind realized that the eighth episode of this season outlined it for us ("Changing Channels" - where the trickster is revealed as Gabriel and demands that they play the parts that destiny has chosen for them, because they so correlate with the Angels' problems. Also, the "it was always you" speeches that Lucifer gave to Sam in the third episode of the season).

It is interesting to see that this was always the case throughout the show, though. A lot of the time, creators/writers SAY they have a clear outline of the arc of a show before they start, but then they change it during or they were lying the entire time. However, Kripke was just that faithful and good to the over-arching arc.