Some actors are extremely talented. A lot of them are. They whittle about in some one dimensional role but they branch out and you realize they can sing and dance very well, also.
Other actors are one dimensional. Tom Cruise plays the exact same role in every movie I've seen him in. Sort of an arrogant over achiever.
Fred Gwynne thought he was typecast as Herman Munster but he was great in My Cousin Vinny and in addition to his acting career, Gwynne sang professionally, painted, and wrote and illustrated children's books. (the last part stolen from Wikipedia)
Hugh Laurie who played House is a British comedian singer.
I think some actors get typecast and then take it as a negative when it's really a testament to how they took a role and made it iconic. So much so, they the public associates the role with the actor.