I can think of few places better positioned for spotting than the Marriott PHL. It is literally positioned within the terminal and it is connected to it and the parking garage complex by air bridges. The hotel is about 200 yards from the PHL Tower.
I had a nice room on the top floor facing the runways. The windows are just impossible to shoot through without major penalty but for the sheer fun and pleasure of spotting from your room, it can;t be beat. And you are very close to the action. The nearest gates/ramp are about 200 yards from the hotel. The runways being a bit further but nothing too bad. 300mm on crop sensor is sufficient reach.
These are just for fun as the weather did not help at all and neither did the dirt and rain on the double windows. There is also an air conditioning unit right below the hotel that every 5 minutes spits out a lot of hot air. Combine with cool ambient air and you have steam condensation ... double bad. OK, some pics. I got to actually spot three specials I had never before seen in person. That was nice.
Oh and the room? I was in Philly for the weekend with the wife and kid, museums for three days. The hotel was only $99 through PriceLine and a total random coincidence as you have no choice when you bid