Just watching "Philadelphia" and I have to say that in my opinion Tom Hanks is the finest movie star of his generation. He's been in many great movies (Saving Private Ryan, Apollo 13, Forrest Gump, Road to Perdition, The Green Mile. etc.) and as regards "turkeys" I can only think of Dragnet (I've never seen either "The Burbs" or "Bonfire of the Vanities").
I appreciate you could also make a case for his co-star in "Philadelphia" - Denzel (Malcolm X, The Hurricane, Cry Freedom, Glory, etc.) however I will leave this to you.