My views on each, in order of likelihood.

Aliens - We will almost certainly find life outside of Earth, it may not be intelligent, but we will find it.
Bigfoot - There is very little chance something like this exists and has gone without being found for so long, especially considering the fact that some people are deliberately looking for it.
Ghosts - It's an extreme stretch to have a situation where the dead interact with the living in incorporeal form. I think we may one day develop a technology to do something similar, though.
God - I don't believe such a thing exists, insofar as people imagine it. Even if our universe does have a creator, it's far more likely that we're the result of a particle accelerator experiment than being the creation of a creature invested in our daily actions. Why would something so powerful even care what we do, when we're so insignificant?

Not god (He doesn't exist)
Not Bigfoot (Everything related to him is fake)
Not ghosts (most things related to them are fake, too)


I say aliens. The Universe is too big for us to be the only living things out there.

I think the next big thing will be that we'll have the technology to explore the deep seas. Currently we've only explored 7% or so of the oceans.

Aliens is a broad term for real things, there are a number of Aliens in Ireland right now, come from the planet Poland.

Sting was an Alien when he went to New York too just to get himself a cup of tea

for those without a taste in music and no idea what I mean https://www.youtube.com/watch?v=d27gTrPPAyk

A Link Between Worlds has rifts you go through to travel to other dimensions. Not everything is from TV.

Edit: Probably God when Jesus comes again, but no one knows when that happens. It could happen after we discover Ghost and Aliens, and make the 1,000,000,001st fake Bigfoot photo/video

Don't you think if there was 'proof of God' it would have been discovered already? So many people spend their lives looking for it. How could ALL of them have failed if it's something to be found?

So clearly Aliens. Or we may find some of the things on earth are actually from other places. We may already be seeing and interacting with aliens and not realize they are alive and communicating with us.

1. Aliens
2. Ghosts
3. God

The rest I don't believe exist

Aliens.

God.