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.

Crazy frog and its sequel were genuinely good racing games for the time. I enjoyed them a lot. Split screen was awesome.