The gameplay in Soul Reaver is probably the best in the series. Well, I'd rate it just below Blood Omen, but whatever - they are sort of different games anyway - SR is more compact, so to say - there is less to do and less to wander around but it keeps it tight, which is good. Essentially, the game gives you limited exploration, in that abilities you get in the game would allow you to visit new areas. Some of these are to advance further, others to just get bonuses from. It's really similar to Darksiders gameplay-wise, if that helps. The other two games from the Soul Reaver arc (SR1, SR2 and Defiance) are simply not as good - while SR2 is my favourite game in the series, it's still essentially a single corridor and you go through it, like, 5 times (blandly) fighting slightly different enemies and unlocking new abilities. Still, the puzzles are nice. Defiance is better than SR2 in gameplay but still not as good as SR1 - the fighting is definitely better but still bland-ish (you have a total of 5 combos, or rather 3 - 2 of those are just "do the same but in the air. And the combos are mirrored across the two characters you play as) and the puzzles are slightly worse than SR2 (well, IMO).
The story is still great across the game, at least.