Characters who were recast, but many people actually prefer the new actor in the role

Tommy Jarvis (Friday the 13th) - Thom Mathews, who played Tommy in Part 6, replaced Corey Feldman from Part 4 and John Shepherd from Part 5

Lord Voldemort (Harry Potter) - Ralph Fiennes, who plays Voldemort from the 4th movie onwards, replaced Richard Bremmer from the 1st movie

The Doctor (Doctor Who) - a character who is frequently recast, but in this specific instance David Tennant, who played the 10th Doctor, replaced Christopher Eccleston, the 9th Doctor