From the PlanetXbox360.com feature editorial:
"Almost ever piece of media, if it sells well enough, will warrant a sequel in some way, shape or form despite the very real underlying need for consistently new content. When Halo was originally designed, it was created as an RTS, for the Macintosh. Well, jump ahead a decade later and Halo has become a monstrous franchise that has brought gamers the world over to their knees and the RTS elements it was build on have gone into Halo Wars. But, when a publisher or developer decides that it is best to ignore new content in the form of original intellectual property, instead focusing on easily marketable titles that a decidedly large market within the gaming community is receptive, the content runs the risk of stagnating. Personally, it is always interesting seeing new titles that push the boundaries of the game experience, illustrating something that players may not have necessarily seen before. While it is fiscally understandable why publishers cling to the cash cow franchises in their respective development houses, however it is the companies that grant life to the untested IPs that seem to acquire a laudable place in the industry and greater player community. Therefore, while it may be enjoyable to have familiar experiences expanded on over time across several iterations, new content is what decidedly develops the medium as a whole."