I have terrain set to low, but textures set to high. Pre set is medium. Visable distance is medium. I've turned off anything I think I don't need. Heat blur and civilian traffic. Just for the hell of of it, I put chimney smoke on zero, too. I'm playing at 1920 x 1080. Runs flawlessly. I don't know HOW you guys are geting slideshows if my weak ass rig is running this the way it is.
One thing I've also done is to set the games priority to high, in the task manager. I think that helps a lot.
Can't play with everything set to high, but I don't care. If you saw my screenshots, it still looks great . To me, anyway.

"From our orbital vantage point, we observe an earth without borders, full of peace, beauty and magnificence, and we pray that humanity as a whole can imagine a borderless world as we see it, and strive to live as one in peace."
Astronaut William C. McCool RIP, January 29, 2003 - Space Shuttle Columbia