Tom Hanks is one of those guys I've had a lot of discussion about with friends.
For me, he's ALWAYS Tom Hanks playing someone. Meaning that I see the ACTOR Tom Hanks on screen, not his character.
It's the same thing for me with Jon Hamm, every time I see him I think, oh it's Jon Hamm.
This is not to say that I don't think both of them are great actors, I just never think they transform into someone else. Not the way a guy like Daniel Day-Lewis or even Leonardo DiCaprio.
As far as Best/Worse:
Best: Cast Away - Props to commanding a screen all by himself, I was interested the entire time. When an actor can get you to feel something for a volleyball, that's a job well done.
Worst: Saving Private Ryan - I found just about every other character in that movie memorable, except for the one Hanks played.