I think if UFOs (alien visitors) did come to earth it would be like something out of Independance Day.
Not necessarily great sfx and an interplanetary war, but it would be on thousands of tv stations across the world with hundreds of thousands of observers.
Running up and down and making beep beep noises in front of lone witnesses seems to be going to a lot of trouble for traversing millions of miles of space. And to what end? A good laugh! Highly unlikely to say the least.

And if they didn't want to be seen - then we havn't seen them.
With the technology we have with stealth bombers and fighters, I can't see how a species that much more technologically advanced than us wouldn't have that capability to - and more so.

What gets me with all these sightings as stated above, is the lack of clear evidence to support them. A bit like ghosts and ghouls and things that go bump in the night.

Yep, you can call me Mr. Skeptic, but unless it taps me on the shoulder with multiple limbs or parks on my front lawn and radiates my grass, I'm not going to be convinced by blurred pictures and a few unsubstantiated reports.

When they come - if they do - it will be the biggest newsflash since man landed on the moon.

__________________
I don't believe in mathematics. Albert Einstein

Biologically speaking, if something bites you it's more likely to be female. Desmond Morris.

Quantum analysis is scientific dithering

Professor Frink: My observations n'hey, n'hey, show the universe could be a torus Weh, uh, or toriod it may like the typewriters and bananas and the monkeys with big teeth the biting the screaming Mm-hai!

Homer: mmmmm... doughnuts!