Looking forward to see what Lego comes up with on the Architectural theme in the future. According to the Lego Architecture site Architecture is Coming Soon. Seems like it will be possible to build the Sears Tower.
I also found John Hancock Center, Empire State Building, Seattle Space Needle on brickstructures.com
There is also a Frank Lloyd Wright Lego collection with Fallingwater and Guggenheim Museum in NY. As you can see they are quite simplified.
And here the Museum in the real world.