For reference:
Perpetuality, the first megagame ever.
Kingmaker, the first megagame to ever finish in a victory.
Careful though, those games can burn people out. I didn't play dominions for months after Perpetuality finished. Guess DrP did me a favour by attacking me in Kingmaker since at least I didn't suffer from burnout again.
And got to kill Niefel Jarls with Markatas.