Anyone who doesn't believe [intelligent] life exists other than on planet earth is an idiot or religious (thus, an idiot). With the number of stars and planets revolving around them.. The conditions for life to emerge will inevitably occur.. For the religious people, I like to ask.. "Why did god create the entire universe if the only space that would be actively used by his creations was Earth?".. It's grandiose to suggest that (if god is real) he created an entire universe for a single creation on a single planet, in a single solar system.

The better question is, "have aliens visited earth?".. Now, that answer is debatable. You'll get everything from 'no, just secret government projects, no aliens' to 'lizard aliens control the governments'.

Who's to say that it's even possible to travel from one solar system to another in a timely manner? And, if it is, and an alien race is capable of doing so... Why would they care to visit some backward redneck planet at the edge of the solar system filled with self-indulgent, self-important bigots?