Having to choose a favorite game would depend upon the chapters of my life. Each chapter had those games that influenced you. Right now, MW3. 5 or so years back? Splinter Cell: Chaos Theory. Back on the original Xbox? I would have to say Halo, but only because it was the hype. For content and story line on the Xbox? Probably Fable and Prince of Persia: The Sands of Time. Loved playing the stories several times through.
Dv