The Parallel Realities website offers a collection of simple, mostly SDL based action games. They’re all fairly lightweight and might make good boredom beaters on a less powerful machine, or failing that, a handy distraction while waiting for something to complete in the background. If amazing graphics are your thing, be warned that the retro styling of all of these games leans more towards nostalgic appeal than an attempt to wow.
The games all worked well when operating in a window, something I prefer when playing a game under Linux. They could all be played via the keyboard, but worked best when used with a dedicated USB game controller.