apparently the sega vintage collection suffers from input lag too. (sonic3)
https://www.youtube.com/watch?v=0OA4xN7__ac
Video could have been a LOT shorter.
I don't see any difference in the video, at least with Sonic. I tried on my own (but with a wireless 360 controller), and don't notice a difference either. I'm playing on a monitor with low display lag, so TV delay shouldn't be an issue. There is a perceived delay when walking side to side, but that's just Sonic's ramp-up time, which is the same on both systems. If there is a difference, it's small, and I tend to be picky about things like this so I'd think it would bother me.
I don't have Mass Effect installed so I can't check that right now. I did try Super Meat Boy, Earthworm Jim HD, Braid, Doom, and Condemned. All seemed very responsive. SMB, EJHD seemed especially snappy with their jumps, and the flashlight on B in Condemned came on with no delay that I could perceive at all. Borderlands is the only disc based game I tried, and it does have severe input lag, but I recall Borderlands feeling really bad anyway, so I don't know if that can be blamed on the emulation. My disc drive on my 360 is messed up, so I can't try the game on there.