Yeah there is just too much stuff that points to intelligent life having visited. I dont believe in crop circle stuff, but some of the cave paintings depicting humanoid figures in space helmets and the quirky knowledge displayed by primitive cultures that had no real direction to developing that particular skill/knowledge, it all indicates that something/someone with a great intellect has shared their talents and skills, Why wouldnt it be aliens.
And if you look at the broad cross section of intelligence displayed by us HOOMANS, from the most stupid dumba$$ to the likes of Edison and Einstein, then why wouldnt that same premise go across the universes.
We think as a race we are pretty clever, but if we are just one point on a scale of smarts, who is above us?