I would say this is a microcosm of a larger problem. In productions like this they go for big names and celebrities over the right actors for the parts.
And you know what as an actor, Chris Pratt has done some fairly versatile stuff. He wasn't always the action hero or leading man. But even with his filmography, him playing Mario just sounds like crack casting.
1. No Mario doesn't need an Italian accent. But that brings us to 2.
2. What does a normal Mario speaking voice sound like? What should it sound like?
In terms of Mario and Luigi, I don't know if Nintendo has this fully established lore or bible for Super Mario Bros., but it's generally accepted that they are from originally from Brooklyn, New York.
Charlie Day is actually from New York, so I guess they can kind of fudge with that. But I mean that's one place to start with Mario and Luigi they may not have been born in Italy or New York, but they were certainly raised there.