Yeah, but with TMNT, they didn't actually advertise the voice actors, now did they. At least initially. And they didn't move the plot, unlike anything Dreamworks has, where the celeb voices are the stars, not the characters they portray.
Personally, I don't way too much care for Spyro, but this seems like it couls actually be a good video game movie, none the less. Hollywood is notorious for making bad bad bad movies based on video games. Look at Super Mario, or worse yet, the horrors of Double Dragon. What was that? Didn't know if it wanted to be comedy or action.
But if theses people are writing the film, I really hope they actually play the games first, and not just pull out random characters or items and then have them open to interpretation.