Slipping under the character's skin and never let audience think whether he lives ...

... real life in general or not is the biggest strength only few posses. Sir Cillian Murphy is one of those rare kind. Generally An actor who comes in the middle of audience multiple times without playing any character losses the ability to mesmerise them, when he finally gets back on the screen eventually. That's the biggest difference they should notice between singers and actors. Sir Cillian understand this more than anyone and resides far away from Hollywood's nocturnal culture. That's what our old time stars well done instead of using their star power on public to manipulate them to buy/participate or constantly updating their life events to flaunt their privileges. Secrecy creates interest, actors always should be interesting.