Half-Life 2 Vs. Halo 2 (PC)

I had a small argument with my friend and he said that Halo 2 will kick Half-Life 2's butt. He also said that Half-Life is only still alive because of the huge amount of mods. I said that Halo and its sequel will die out quickly due to lack of a mod community but he refused to listen. Maybe some hard evidence on this site will prove him wrong. maybe... So: WHICH WILL BE BETTER OVERALL? (I added some more choices which you may choose)