I believe life exists off the planet. I am uncertain on whether or not intelligent Alien life has interfered with Earth, I'd say it likely has not, and it's all just our imagination just like with Ghosts and Demons.
Ghosts and Aliens are not the same level... I dunno It's becoming more and more interesting who's saying they're visiting. These guys are not just the wierdos we're used to hearing from. I have no doubt they exist I guess like you say it's just do they visit here.
If they have visited I don't believe it's physically. It would be through remote controlled drones and ships of their own. Its one thing sending a drone millions of miles but sending another being physically? Not sure.
I have to say I find it hard to believe they'd travel this far bending space and time and then crash into a mountain. I do think it's possible they're closer than we think possible mind.
I have no religious belief but I believe the universe will be teaming with life of all descriptions just based on the numbers. Whether one or more civilisations come here is another thing ,but it's high ranking Government officials, pilots and astronauts saying they do so I'm starting to believe they do. To them we might just be like an ants nest in the woods.
With Tash on this one, aliens 100% exist but if they are intelligent enough to reach us is the question. If it wasn't for the asteroid that wiped out the dinosaurs we wouldn't be here and its certain there is other life out there - I would bet my house on them finding some life forms when they start drilling into some of the icy moons in our own solar system - like planktonic life forms but life forms none the less. The question I always struggle with is - are we the most advanced? Personally I'd doubt that because of the infinite possibilities in the ever expanding universe but in the grand scheme of it all, the universe being an estimated 25-28 billion years old and earth being 4.5 billion years old, we are on a pretty old rock, in a Goldie-lock zone and had 5 mass extinction events which have not destroyed the planet - so we actually could be.
They have pretty much confirmed life existed on Mars already and that the probability of life elsewhere is more than likely. There's also other dimensions to consider and the possibility that it's actually humans visiting earth from the future. The possibilities are endless to the point where ruling anything out is more bewildering than keeping an open mind.
Ahh mate love all this stuff but the other dimensions and bubble universe theory's etc is where it just melts my mind - to much for our mouse brains to comprehend!