i agree with the_artist it's a little unfair when comparing the two as far as graphics. When it comes to plot and overall action though i'm going with Halo.
I haven't played prime yet, but I doubt it can measure up to the battle in a corridor of the Pillar of Autum(last level,Maw). The Flood, the Covenant, and the Monitors Drones all in the same corridor fighting.
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