Do you mean voiceovers for stuff like animation or voiceovers for movie trailers/commercials/etc? Because voiceover for animation isn't something everybody can do. I've heard a lot of great actors do voiceovers for animation and they just don't fit. But this is assuming that you were talking about VO for animation.
Let me be more specific. The greatest of the great can do EVERYTHING (VO, commercial etc etc and they can play all kinds of characters). Then you have your actors who are generally speaking great (like they can do different character types and do more than one or two mediums in the acting world, successfully). Then you have your actors who are great at doing one character type/acting part (They are great at playing a certain role like the gangster or the hero. Or there good at being a lead vs being a character vice versa) These are VERY ROUGH generalizations (Im too lazy to get in depth lol) of the grading of how good or bad a actor is. Most actors are a mix and match of sorts (in both the medium in which they can and cant act. And in the actual character(s) they can and cant do). Like theyre great at playing the hero, lead, voice over, but suck at being the lead, hero, in feature films. Or there good at playing the thug, but they are horrible at anything outside of that character type.
Can't come down hard on him. He's playing roles he feels comfortable in. What he's done in real life. I'm waiting to see him in the role where he has cancer? That will test his dramatic abilities. His body is off the chain. Crackhead or not, he was doing her good, lol!