If Cube were to remain the same in his movies he wouldn't be making a real strech as an actor.
Wanting Ice Cube to continue to play roles like his previous ones is just stupid IMO. That's like saying we want Al Pacino to replay Tony Montana, Frank Serpico, Michael Corleone etc etc... in every movie for the remainder of his career.
Ice Cube embraced us with his gangsta raps and took us through his movies. Now, he's embracing our kids and expanding his fan base as an actor. That's a true meaning of longivity. Much like Will Smith who played serious roles in "The Pursuit of Happyness", or "I Am Legend" etc etc...
Adam Sandler even played his first serious role (in a movie which escapes my mind right now), but I think wether your an rapper, or comedian it's always nice to see them move forward in their careers. The point being that people are not used to seeing them for who they really are (entertainers). People are stuck on the charaters that they portrayed early in their careers. Things change and people grow up and move forward.
Wishing for any actor to remain the same in every movie is pretty much wishing for every movie they're in to be a direct to DVD release.