ODST.....
Halo ODST is far from a "meh" kind of game. The biggest issue is the lack of matchmaking on firefight. Having to invite a friend to the game is sometimes a good thing to get the scrubs/noobs out, but then again it's an annoying thing if none of your friends are playing the game or if they traded the game in.
I did in fact enjoy the single player like other Halo games, but due to the fact that it just feels like a spin-off, which in fact is a spin-off. Makes me feel like I'm not progressing much in the Halo story. Halo has a deep story and gameplay that is not only fun, but is addictive.
The game also has another disk that has Halo 3's multiplayer and all DLC. If you don't own Halo 3 or your Halo 3 disc got scratched or haven't bought any DLC what so ever, then this game should be picked up. If you can't find Halo ODST (I doubt you can't, because it's Halo), you can get it on sale over the internet for REAL cheap.