Crackdown 2 is ok, but not as good as the original. The core gameplay there is still a blast, there’s just not as much going on. It’s pretty much a sandbox for blowing stuff up - if that’s what you’re looking for, you’re good. Just note that it isn’t backward compatible on the Xbox One yet, if that matters. Folks are speculating the two Crackdown games will be released to back compat around the time 3 is released.
I like the Missing Link DLC for Human Revolution, it’s a little self-contained side story. I really liked the base HR game so I would imagine that’s going to be the indicator as to how much you’ll appreciate the DLC.