What else do we need to say here. Simba is the hero and main character from the Lion King Franchise. As an adult, he dealt with many issues surrounding the death of his father including fear and guilt. Eventually though he would take his place as the true King of the Jungle.
Before we get into my picks though lets clear up who voiced who when for those out there not aware, and because it can be confusing at times...
As for the adult version of this classic character, it started out with Ferrie Bueller, I mean Matthew Broderick doing the speaking voice in the movie, while son of famed composer John Williams, Joseph Williams, provided the singing voice. Broderick also voiced the adult version in both Lion King 1 and 1/2 and Lion King 2.
Cam Clarke is the only other voice actor to take on the adult role of Simba, which he did in the TV Series, Timon and Pumbaa, as well as in the Kingdom Hearts game. Interestingly Clarke also provided the singing voice in the movie, Lion King 2.