A better example is Bigfoot, with the millions of game cameras out in the wilderness. Seems by now someone would've captured something.
If anything exists though, it's aliens. A big as this universe is it'd be pretty pretentious for us to think this one tiny planet has the only life. Even if you believe God created us, who's to say he didn't do the same somewhere else?
That's not to say they're visiting us, and it's not to say they're more advanced, or possess any other of the stereotypical alien traits that were made popular by 'B' science fiction films. They could be less advanced and stuck on their planet. They could still be climbing out of the ooze, beginning their journey of evolution. Still, I think there's a better chance than not that there's life elsewhere.