Savetehaloz reviews the most overrated game to hit the Xbox console.
Another complaint is the ugly cutscenes. Typically, cutscenes are on par with the gameplay itself, but not in Halo 2. When a cutscene begins, you'll see textures coming to an apropriate resolution; like real time rendering. And it usually takes a second instead of instantaneous loading. The cutscenes are also blurry and the edges around the characters are choppy and the textures are also pretty washed out.
Level design (especially on the alien levels) is pretty repetitive with so many closing and opening doors that I get really lost (and bored to).
On a positive note, Halo 2 features a battlerifle to replace the all powerful magnum from Halo Combat Evolved (thank god IDK how people could get away with one shot pistol kills :[ ) and a toned down pistol.
It is recommended to buy Halo 2 as it makes a worthy addition to anyone's Xbox collection and it is probably required if you are following Halo's story.