It all depends on what type of gamer you are...
I love to play Rock Band because it is a party game and everyone can get into the game. You can start a band online, new songs, and if your not getting the instruments i assume you have played the first one so it isnt a new ip for you to play.
Halo wars i have mix feelings about, I love Rts games with a passion... But this game makes me become mellow and very dull it is a watered down version of star craft. Many times have I sat on the floor in front of my tv feeling like i didnt want to do anything, Now dont get me wrong when you do get into it with your friends it is fun. But the fun does not last long when you realize your army is capped at a very lower amount, and you arent allowed to use features such as walls, turrents out side of your base, and other little things.
I would suggest Rock Band 2 because it is a strong game with more replay value then Halo Wars, and During this recession the best is to get the most bang for yourrr buck.
