It is really hard for me to play through the modern Deus Ex games.  Probably harder than it is to replay Thief 4, because Thief 4 was just *bad*.  There are no redeeming features in the game design and I can mostly just close my proverbial eyes and force through once you've seen the first mission or so because it starts as it means to go on.  Human Revolution has enough good going for it that I want to like it, but I just can't.

None of the people acts like a human being would.  They're walking anime tropes, and bad ones at that.  When I can't relate to the way anyone is acting towards anything, I can't find myself involved in the game world, and when you're building a game based on narrative, that's a cyanide pill that kills everything else.  And divorced from the story, you just have a very painfully average shooter with floaty controls that covered everything in a piss filter.