If the universe is infinite, then there are infinite possibilities....
It's easy to see how small the world is when you think about each star being the centre of it's own planetary system. How can people think that there is no life out there? This one planet circling this one star that even amongst just the stars that we see, makes it impossible to know how many planets are dismissed as possibly sustaining life. Is it because they haven't stopped by for a personal visit? We haven't exactly hitched a ride across the milky way with google universe, turn by turn directions to the nearest alien wold.
Even if interstellar travel - you know, that kind that didn't take few life times to get there - just happened to meet its discoverer tomorrow - We could visit thousands of planets and we still couldn't say it proves as a fact that is no life out there. If life was found, without being able to ask them if it was a good spot to park the shuttle or if whether not having a permit would get you towed, would hardly be the worst case scenario. I guess a little spying would take place, maybe a friendly autopsy or perhaps a little trap, test, tag and release.. I actually would hate to think what we would do if we found them first. Would science fiction have it right with warring species, defending their planets? Perhaps there are others with superior technology sitting it out, not wanting to get involved with the third world planets political issues.
Regardless if you flat out don't believe it, how do you know for a fact? - Because others said so, or is it because you haven't seen it? Few can claim to have seen god, yet that belief to explain a win, good fortune, health, prosperity and luck is not just the raving assertions of a madman but a global collective. Who knows if any religion has it right - What if god had a family and as a kid, got sent to his galaxy without dinner and thought he'd take a crack at creating life just hoping the worship and praise would make him feel better. No one wants to think we are just his elaborate version of Sim City waiting for the day he comes back; what if he has grown up, had more practice and created another world where, being immortal, he created a life form that lived for a few million years. A species that could follow instructions, didn't give lip or keep making the same mistakes so he gave them superpowers and they could turn their own water into wine.
OK, so that's probably not an idea that is going to catch on. Even less popular though is the belief that when you die, that's it - your conscious no longer exists. It's not possible to imagine because you imagine how it would feel but the problem with proving if there is life after death, is pretty much - you're dead. You may be in a better place, you may be in another place thats pretty much the same but with a whole lot more people, you may just be at level 2 and this time you're born with wings....
I don't think anyone has quite got it right. But no matter what god someone believes in or if there is life out there, people are what is wrong with the world and people are what can fix it. If we did get a visit from god, or an alien just decided to check out the beaches - Even on what may be the cynically slim chance that the reception would be pleasant, do you think they'll like what we've done with the place? If they've been watching for while, checking out the whole world, I wouldn't be able to say with much certainty that the answer would be yes for neither god nor alien. We might be able to say we are a good person but can anyone honestly say that as a species, they'd invite us back to their place and say "treat yourself at home"?