Listen to Mario talk on Gameboy Advance games. Charles Martinet is a nice bloke but he's just some guy they hired for Mario 64 who stuck around. He's over 60 years old and hasn't got the range to pull off Mario talking like would be needed for an actual movie. Sort of like how Walt Disney was kind of a terrible voice actor for Mickey too. But his current voice actor is fantastic.
Give Charles Martinet a nice role like father of Mario or something.