I've always been more a fan of post-apocalyptic. Who cares about billions of people running around like drowning rats? I'm much more the "let's see what the survivors are doing with the pieces" kind of guy.Special exception for Zombie movies. But a massive outbreak is usually a post-apocalyptic flick in any case.
But basically you have
War
Disease
Natural Disaster
Unnatural Disaster (End of Days scenario)
And those go all the way back to the 4 horsemen and further. New twist gets tough after awhile without relying on new tech doomsday or old story FROM SPACE....space...space...or another dimension/parallel universe.
Well that and cross pollinating the 4 things.
Honestly though a good apocalyptic movie is one where not a lot of people survive. Most disaster/end of world flicks are a little more optimistic for a happy ending kind of thing.
Me, I'm sick of natural disaster movies because they never get any of the details even half right. It hurts to be a geologist watching that stuff.
Bring on the Space Invaders, Andromeda Strains, Demons, Zombies, and Nukes!