At the end of the day mine is IVAN.
It's maybe the only roguelike I regularly return to just to play for fun even though I've already gotten the best ending.
I don't really know what it is about that game that keeps me coming back. It's not very balanced or fair, but it's also one of the least frustrating rougelikes for me.
Part of that is probably the character design process, where you make your guy with just what the dungeon gives you.
I wish more roguelikes would dump the classes in favor of something like this. It actually makes the early-game interesting instead of insufferable.
Since I will end up spending a lot of time in the first few dungeon levels, it really helps to have something so it doesn't feel like I'm just going through the motions.