Ridley Scott isn't overrated. He is one of the most influential directors of our time and he is one of the very best in innovation of amazing visual effects. He has made more consistently good films than many people give him credit for.
Best of all time I would say Alien, Blade Runner, Gladiator, AND Kingdom Of Heaven (DC), and I think you can be damn sure Prometheus will be the 5th.
And Great ones... Thelma and Louis, Black Hawk Down, Matchstick Men, American Gangster
That's 8 solid films, a few of which are SUPER GOOD. Besides that, he has some stuff that is good but not amazing like Body of lies, Hannibal, The Duellists.
Besides that, he has had a few very low moments, but it's not too numerous. Ridley experiments. He is famous for Sci Fi and Gladiator, but the man has done Historical epics, modern War movies, weird drama's like Matchstick Men, crime drama's like American Gangster... etc. I think just for making very successful and great movies in all those genres he deserves gets a lot of credit for being able to experiment. He has had some pretty bad experiments like White Squall and the go awful GI Jane, but he has had more successes than failures.
"I'm not afraid... I'm angry."