OK, 1) what makes you think there are aliens out there? We've had some good imagery of the Solar planets lately, and guess what? No signs of live. And 2) Earth has been around for millions of years and we still don't have prove of aliens visiting us. What are the odds we will see any in the next millions of years? Further more 3) you have been watching too many SciFi movies and TV programs that you are forgetting the facts!
Although it would be cool to see an alien one day, but logically and statistically speaking it's almost impossible.