Final Level: Chronoplast
Why It Sucked: The worst kind of cop-out is when the ending leads straight into the beginning of the next game, with zero resolution and satisfaction. That's exactly what happens in Soul Reaver: Kain. The final boss, even says, "This is not where or how it ends."
How We Would End It: Obviously, we would have liked to see more of a resolution and less of a "See you in the sequel!" mentality.