If your not gonna get halo, then wait for black ops, MW2 is an amazing game but Black Ops looks so much better. I havent played Reach, but when I get Black Ops, im gonna be waiting to buy Reach lol. Reach does look epic and Forge world looks insane. Its down to you really. I prefer CoD's multiplayer so I'd say that.
They are both great on live BUT Reach has a horrible campaign.