Okay, yes, both games have been out for a few years. However, if you’ve either never played either games, or would like to have it digitally so you don’t have to worry about losing your disc, then NOW is the time to buy!
Halo Wars is on sale for the LOW price of $4.94!!
Here it is on the marketplace: 
You can buy that here: http://marketplace.xbox.com/en-US/Product/Halo-Wars/66acd000-77fe-1000-9115-d8024d530808?nosplash=1&DownloadType=Game
Halo Reach is on sale for $9.89. A pretty decent price if you ask me.\
Here is that one on the marketplace: 
And here’s the link to it online: http://marketplace.xbox.com/en-US/Product/Halo-Reach/66acd000-77fe-1000-9115-d8024d53085b?nosplash=1&DownloadType=Game
or of course you can buy either/both through your XBOX 360.
I’m not sure how long the sale is for, so get it while you can!
-Sal