Soul Reaver offers a varied style of gameplay that is largely absent in today's games and an unparalleled story.
While later iterations in the series become increasingly complicated, the story of Soul Reaver is a straight-up story of revenge. You play as Raziel, a vampire cast by his "brothers" and his creator Kain into an abyss. After ascending from the abyss with the aid of a mysterious benefactor, Raziel has become a devourer of souls and he sets about killing his treacherous brothers and consuming their essences in order to gain new abilities before he goes to confront his former master.
Soul Reaver is a much more open-world experience than any of its successors and I am inclined to think it was better for it. While Soul Reaver 2 and Defiance were very linear games Soul Reaver offers you the freedom to explore and find shrines which imbue you with spells and even a fire enhancement for the symbiotic reaver blade you acquire.
Combat is also more engaging in Soul Reaver. Your vampiric enemies will quickly recover after taking damage. In order to defeat them you will need to beat them into submission, destroy their bodies and then consume their souls. Soul Reaver offers many means by which to accomplish this. Vampires can be hurled onto spikes, or into water or sunlight or even burned to a crisp using torches. Early in the game you also acquire a wraithblade that can easily destroy your vampire enemies but you can only use this weapon when you are at full health. Later in the game you also gain the ability to fire telekinetic bolts that are especially effective when enhanced with the fire reaver.
Soul Reaver is, however, an older game, and players used to newer games may have a hard time appreciating the older graphics of Soul Reaver, especially because the character's mouths don't move when they talk. If, however, you can bear the older graphics, you will find that the experience Soul Reaver offers competes with what any new game can offer.