I haven't played either one, but I bet that COD is better because I don't see any new MO: Honor games released.
Call of Duty series. Simply because of Modern Warfare. However the MOH series are apparently rebooting with a new game coming out next year: http://en.wikipedia.org/wiki/Medal_of_Honor_%282010_video_game%29
I'd say COD, but MOH has my nastalgia (i dont know how to spell that) rating. Call od duty is far more advanced obviously, so it depends on what games you are comparing.
MoH is generally lame. CoD 4 and 5 are fucking ruined by Marty, Jugg and Secondary Wep System. MW2 totally screwed up with Killstreaks and camping stuff. CoD2 > Other CoD's and MoH series