Games that play like the concept of Ragnarok.
We're not talking about games that mention Norse mythology. What I mean are games that get more intense as time goes on. A game that no matter how hard you try, or how well you're doing, you're screwed. The game will end and you will have LOST. The game is unbeatable. No amount of training in Valhalla will do you any good. This list cannot include games with a "kill screen." That's like telling the game you're even with it. No, this game must inevitably crush you, but be fun enough that you try to beat it over and over again.
3 more things:
1) These games can't have stages that change once you start playing them.
2) They can't end because of a timer, they must end due to death.
3) You must be overwhelmed by multiple opponents at once, they generally increase in number the longer you survive.