That would be amazing, but since the entire series is done with voice acting (and all of the same actors do all of their respective characters in every game) the game series is already very much like a movie series. If someone were to make an actual theatrical motion picture, it would have to be done completely in CG, like the Final Fantasy movie.
The characters would have to be voiced by the same actors from the games though. I wouldn't even consider watching it if Simon Templeman and Michael Bell weren't doing the voices of Kain and Raziel.
I doubt it very much. It would either cost WAY too much to make a decent movie, or they would spend a lot less money and make a really poor one. The series isn't quite big enough for anyone to want to invest that much money in a movie about it. Look at how long it took Mario Bros. and Final Fantasy to get a movie. It took forever, and most people were very disappointed with them.
I'm having a hard time deciding which series I prefer: Legacy of Kain or Final Fantasy. I've been playing Final Fantasy games for ten tears, and they rarely ever disappoint me. But, the Legacy of Kain series has SUCH A BADASS storyline, and both Kain and Raziel are two of the coolest video game characters EVER. I just can't decide!