When Halo was first released it was a great game, but many sequals later and it has gotten worse each time, mainly due to the fact that nothing innovative has been added. Call of Duty 2 and 4 are the only good versions of the game, releases like Modern Warfare 2 and 3 have ruined the online gameplay, story is not bad but could do with much more work, and they have used the same engine since Call of Duty 4 for four of the sequals. On the other hand Battlefield 3 is a great game, they have added many features, and a new engine, with much more interesting gameplay.