With the news of an Danny Phantom live-action movie project. I tought of a wishlist of actors who could play the following roles. Note then it's more of a pipe-dream fantasy then a real list.
Danny Fenton/Phantom: Justin Long, he played a unlucky high school student in "Dodgeball" and I think he might fit the role more then Drake Bell.
Sam Manson: I go a bit outside of the box for this one: Cherie van der Merwe, an actress from South Africa who starred in the movie Bakgat. [link]
Tucker: One Youtube user mentionned Tyler J. Williams [link] and I gree with the user's choice.
Jack Fenton: I got 2 choices; 1st Kevin James or the 2nd choice, French-Canadian actor Remy Girard.
Maddie Fenton: Christine Taylor
Jazz Fenton: Julie Gonzalo
Danielle: Missy Peregrym, a Canadian actress [link]
Dash Baxter: Trever O'Brien
Kwam: Doua Moua [link]
Mr. Lancer: Marius Weyers [link]
Valerie Grey: Kyla Pratt
Mr. Grey: Ernie Hudson
Paulina: Camila Banus [link]
Vlad Masters: Alec Baldwin
Dark Danny: Matt Damon
Edit: I forgotted to mention Sam's parents: Jeremy and Pamela
Jeremy Manson: 1st choice Kevin Sorbo, 2nd choice Matthew McConaughey
Pamela Manson: Kate Bekinsale
Grandma Manson: Sandra Prinsloo [link]