I'm sure everybody has seen his spectacular acting ability in Forrest Gump and that is just one of my favorite Tom Hanks film. Unfortunately, when you have a new favorite actor, past favorite actor or a good actor in general, it is hard to differentiate and choose between all of their movies and pick one as their best in your own opinion (or at least for me).
I really enjoyed his talents in the Disney Pixar series Toy Story (if that counts) as the voice actor for Woody (the cowboy).
I also liked him in one of his least favorite films (or so I am guessing since most people don't mention it more often), Lost in Translation, also starring Scarlett Johansson. It is a great film for those who just want to sit around, eat popcorn and enjoy amulticulturall flick with good humor and realistic depth.
I also agree with you on Philadelphia 100%
Here's the IMDb links for the movies I listed:
Lost in Translation: http://www.imdb.com/title/tt0335266/
Toy Story (1): http://www.imdb.com/title/tt0114709/
Forrest Gump: http://www.imdb.com/title/tt0109830/