Blood Omen
Blood Omen 2*
Soul Reaver
Soul Reaver II
Defiance
*The game is set between Blood Omen and Soul Reaver but is explained away as some alternate universe later in the series - breaks canon if I remember right. Personally I think it's better to skip BO2, not a fan of it in the slightest.
Technically, Blood Omen 2 happens after Defiance.