I would say Tom hanks is one of the best actors that i have seen..... he was simply superb in Forrest gump.. Incidentally being a tamilian i have watched almost all the movies of kamal sir, still i would rate tom hanks at the top...
Easy - My all time favs are Morgan Freeman, Clint Eastwood and Denzel Washington Perfect, skillful, appealing, can do any role and draw you into believing their character Honourable mention to the late Heath Ledger (RIP) for his role in the Dark Night - Unbelievable and scary good
The actor who can take on any role and do a brilliant job of it. When I think of actors with diversified roles Robert Deniro and Heath Ledger come to mind. I'm sure there are many other brilliant actors.