360 Games

My team at work gave me a £15 gift card for Game as a birthday present which was a really great surprise. However now I need to decide what to get with the card! The options I have are:

• Fable 2 - Bro has it so could just borrow off him
• Dead Space - Bro also has this so could just borrow it once he's done
• Fallout 3 - Never played the first 2 but everyone's raving about it
• Mirror's Edge - Supposed to be fantastic but not out until the 14th
• Red Alert 3 - Looks really good, but the 360 version also isn't out until the 14th
• Rock Band 2 - I never got the first Rock Band and now the second one is out in a month and could be a lot of fun. The instruments don't come out until December however and it'll cost a LOT, which isn't really sensible when I've a holiday to pay for in January

Or I could just get a 2100 card to get the arcade games which always seem to be great value for money...

Too many good games for the 360 out recently! Any recommendations? :P