I love this one. The banter/commentary with Zip and Allister really adds new life into the games story. It's also the perfect length in my opinion, with a lot of variety of perfectly designed locations, and a really smooth difficulty curve.
Incredible level design. Here, they take it to a whole new level of emmerisiveness. The game also serves as the dramatic climax to the story started with Anniversary and continued in Legend. It does not disappoint!