Halo 3:ODST or Call of Duty: Modern Warfare 2?

Wow great question, you got me there. Well, I am getting Halo 3: ODST first as I am a BIG Halo fan. But Modern Warfare 2(MW2) looks sick. But the great thing to know, is that Halo 3: ODST comes out September 22 and MW2 comes out November 10. So I will save up enough money to get both! Hope you keep that in mind.