Have you checked out XCOM: Enemy Unknown?
Herk's forum posts
I almost never play a game after I've finished it so the only time I can even remember doing it was with Fez, and it's because it felt like the first ending was actually just a mid-break on the way to the actual finish. Which it also was.
I played some game where you were an archer on the left side of the screen and shot baloons that came up on the right on different formations. I have no idea what it's called and it would be awesome if anyone recognizes this and knows the name.
The first game I played that I also know the name of is Earthworm Jim on the SNES or some of the real early NHL on PC.
It should not be impossible to make it a challenge while still awesome to play. And I've never played Dark Souls because it seemed unfair but you and a lot of other guys describing how fun the bosses are makes me wanna try the second one!