I really want to play single-player versions, or at least on my own private server, games like Travian or Ikariam. Basically resource management strategies but without the insane need to be 24/7 online in anticipation of an enemy attack.
Edit: Also a single player tab targetting open world rpg.
How else would you test the difference? By looking at a still picture?
The difference matters very much in high speed video games and this is the most basic of ways to test it.