I sold Grid a long time ago, but at 400 MSP I decided to get the on-demand version. Grid 2 comes out in May
My coworker praises Halo Wars, but I don't feel compelled enough to pick it up :/
I would pick it up if you like the Halo series. I know its an RTS, but its simplified enough that it feels fresh to play it on the Xbox and it controls well. The campaign alone is very fun, you get to use a variety of units in the Halo universe, and the story is a prequel to Halo 1.
I enjoyed this game tremendously, it was only years later that I realized how much I enjoyed it (one of my favorite games this gen for sure, I own it twice on disc, standard and Platinum Hits version). Now I pretty much bought a PC just to play RTS games like Starcraft 2, but Halo Wars started that.
On the sales note, I picked up El Shaddai (rented it once, wasn't impressed, but at $3, its a no brainer), Dark Messiah and The Darkness. I pretty much own 99% of all the games that are on sale, but will pick some up if they are dirt cheap, are old (cause finding physical copies is harder), or want a backup copy on Xbox. I buy them with the idea that they won't transfer over to the next gen Xbox, that way, I'm preparing myself mentally and not raising my hopes.
Now playing: Diablo 3 (360), Lost Planet 3, Saints Row 4, Rayman Legends, Killzone Mercenary, Starcraft 2: Heart of the Swarm.