Gotta go with Dragon Age, but only because I've owned it longer than Mass Effect (PS3 gamer here). On my third ME2 playthough and probably starting a 4th soon, so yeah.
Dragon Age had Awakenings, so even though I've only played through that one 3 times, I've still clocked more hours in Dragon Age than ME. But ME is catching up. And with ME3 in March, the ME time should match or exceed Dragon Age - at least until I play through Dragon Age 2 again. ^^