This is going to sound strange, but the monorail (taking you between terminals and to/from the car rental and long term parking) has some pretty fantastic views. The disadvantage is that it's a moving platform over which you have no control. As long as you're ok with that, I recall getting some nice views of departing traffic from the 28's and 1's.
You would just hop off upon reaching the last terminal, then hop on a train going the other way...repeat until bored.
Another spot is the long term parking lot for heavy 28 deps. They come pretty much straight overhead.
There used to be a phenomenal spot at the 1R numbers that would blow your ears off when an MD-80 would leave but they discontinued access a while ago. It's a shame. When my gf (now, wife) and I were dating long distance, I would drop her off at the airport, hurry into that 1R viewing spot, fire up the scanner, and wait for her flight to leave.