Let's not go crazy here. Gus always has this effect. The character, his story, and the way his little section is written, are bound to. Yes he was fantastic, but having an old man with a notably weak-soundng voice, wobbling through a soft song about his old theater days... this is very different than the rest of the characters and songs.
I don't want to take anything away from him but it's not like he got this reaction from everyone somehow while playing Bustipher Jones or Macavity.