I can think of a handful of games that, despite being games that I’ve enjoyed, never really became part of a “genre”. Do you have any like this, and if so, which?
Are they games that you’d like to see another entrant to the genre to? Would you recommend the original game as one to keep playing?
It’s quite common in retro shmups, particularly bullet hells putting way too many sprites onscreen. Designers were always aware of it and intentionally balanced the difficulty around it, and some later games even include artificial slowdown just to preserve that feel.