Zakk Wylde's a great singer too, with a strong emotive blues voice. Check out his album "book of shadows", it's much lighter than his other albums, having a kind of acoustic/blues rock feel. There are some great songs on it I think, I prefer it to the live album I have of his where he plays in a metalic vein.

Personnally I think that Malmsteem is a slightly superior player but his music (aside from some blinding solos) I generally find cheesy except when he does acoustic sets in pseudo-classical style.