I think that ending 6 is the best ending, cause it gives Felix fresh start on life and gives him experience to be more observant in the future. Instead of blank page ending, i would have called it rational ending.
I think my favorite endings are
1.Alone(one where everyone moved on while he's still stuck in the past on sophie, that one was depressing as hell but honestly was the most entertaining)
2. A Blank Page (funnily enough just as number 1 was Felix at this lowest, Blank page is him at his highest, and simply a well-deserved high so that's why I like it)
3.A perfect balance (I think its called anyways, that one where you know where everything is going to go to shit and get messy as hell the second Zack leaves yet they leave it on such a "happy" note Sophie remains the "faithful wife" in Felixs eyes, while also being a turbo slut with not only Amy but Danielle too)
Honorable mention: the abrupt ending when Felix pushes back against Zack and we get no real NTR and Felix and Sophie move away (IIRC) and still have a baby together (that's more like a parody ending but still this technically him at his real highest)
Dont really like the ending where Sophie gets pregnant with Zacks kid but stays with Felix cause the sudden "oh I feel bad for cheating on my husband" felt too abrupt for me, at least with Gangbang endings Sophie it was before she went tooooo far off the deep end
All in all I think the games is pretty good