I agree, they don't semm likely.
Now not saying I don't believe in intelligent life outside our solar system (the chance is 1 to 500000000000000000000000000000000000 [5 with 35 0's] that there is none anywere in the universe). It is just that seeming logical a race more advanced than us if it had found us, wound either conquer us and enslave us for there greater glory or make themselves known to share there knowledge.
Put yourself in the shoes of a superior race, if you are somewhat conquering inclined then earth would look fairly easy pickings, if you were peacefully inclined or trade inclined you would tell the whole earth in one step so as no-one would be left out of the loop (so to speak).
The idea that we are just being monitored and have been for years does not make sense, the human species lives year to year almost the same (minor aesthetic changes) the most they would have to monitor us for would be a year.
I more off the opinion that it is the govenrment, but not in the coverup, testing on there own citizens way. Just testing there new gizmos, and maybe letting blame for bad things lay on aliens. But then denying there existence.