The Diablo 3 main menu has a Cinematics button:
Where you can choose to view cinematics you've unlocked:
Except you'll notice there's no option to view Tyrael's Sacrifice again.
Where's the option to view Tyrael's Sacrifice again?
https://eu.battle.net/d3/en/forum/topic/4209931810 This forum solved this issue for me, i was missing tyrael's sacrifice - the best cutscene!
Open My Documents\Diablo III\D3Prefs.txt (for win7/vista, not sure where it is in xp or os-x) in notepad and change the "PlayedCutscene" lines to (or add them if they are missing)
I just figured it out.
Cinematics are unlocked per computer.
I just started Diablo on my work machine and only 3 cinematics are unlocked:
I guess this is part of Blizzard's online only and offline only system. If i want access to the cinematics I will have to start over and be sure to not play at work.