Here are my picks for the cast:

Hugh Jackman-Sephiroth
Michael Johns (American Idol 2008 finalist)-Cloud Strife
Carly Smithson (American Idol 2008 finalist)-Tifa Lockhart
Hayden Christensen-Vincent Valentine
Adam Gontier (Three Days Grace vocalist)-Zack Fair
Holly Brook (singer featured in Fort Minor)-Aerith Gainsborough
Wyclef Jean-Barret Wallace
Devon Aoki-Yuffie Kisaragi

Even if they made another CG movie like its sequel Advent Children, I'd still like the characters to look like and be voiced by the above selections.