Well the graphics in Halo were excellent, and the graphics in Halo 2 are much better, so I'd have to day that Halo 2 has great graphics.
I actually think Halo's biggest achievement was in sound. The perfect sound effects with dramatic music chiming in at precisely the right moments. Whe your adrenaline starts pumping because you hear a certain kind of music in a game, thats an exellent job.
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