Fun game!
As others have echoed Philly lacks really tall pre-war buildings. The long standing gentleman's agreement kept all the old buildings below 500 feet (and somewhat indistinguishable when viewing the skyline as a whole); our tallest buildings are all modern. To that end, I'd add:
Terminal Tower (Cleveland)
40 Wall Street (NYC)
Metropolitan Life Insurance Building (NYC)*
Note: I actually prefer Chicago's Wrigley Building over Met Life, but at just 438 feet, it wouldn't stand out as much in Philly.
I also think Philly's tallest modern buildings are a bit safe/conservative and would like to add a couple to jazz things up a bit:
Turning Torso (Sweden)
The Shard (London)