What are some alternatives?
When comparing Cave Story and Nikki and the Robots, you can also consider the following products
Hollow Knight - Descend into the Dark Venture down into a beautiful, ruined world of insects and heroes
SuperTux - SuperTux is a classic 2D jump'n run sidescroller game in a style similar to the original Super...
Super Meat Boy - Let's start with what's the same: Dr. Fetus is still a jerk, gameplay is super challenging but fair, there are tight controls and great levels and you will die. a lot.
Braid - Resource planning & scheduling for professional services
Secret Maryo Chronicles - Secret Maryo Chronicles is an Open Source two-dimensional platform game and is using an Open Graphics Library for the best possible graphic design and stock performance.
Limbo - “Dark, disturbing, yet eerily beautiful, Limbo is a world that deserves to be explored.” Joystiq. “Limbo is as close to perfect at what it does as a game can get.” Destructoid. Buy LIMBO: Special Edition.