Dead Rising can take you about 8 hours or so to beat, if you just stick to the main story and dont do side missions. Elder Scrolls IV: Oblivion is a great bang for your buck. I had over 200 hours put into it and just got done with it before I sent it to its new ower. GOTY edition is well worth the 900 points. You get the game plus the 3,200 Microsoft Point Downloadable Content with it, Knights of the Nine (800 MS Points) and Shivering Isles (2,400) which is about $40. So Elder Scrolls IV: Oblivion is my recomendation.
Elder Scrolls IV: Oblivion Xbox 360 Game List Goozex
3 of the listings, 450/500/900, are the full games. The other 2, 150/500, are the Downloadable Content that would come with the GOTY Edition of Oblivion, the 900 point one. The 500 Point version is the Collector's Edition which has: This collector's edition of the RPG epic features a bonus DVD featuring
a behind-the-scenes documentary on the making of Oblivion, plus concept
art, and renders, screenshots, and other extra features. Also featured
is a Septims replica coin, and a 112 page "Pocket Guide to the Empire"
featuring historical information, important figure profiles, and other
realistically rendered details about the The Elder Scrolls saga.
So it is up to you to make a choice, Dead Rising is a quick get due to ALOT of people have it for trade. Oblivion is a great game all around and has alot of things to do in it.