game ideas are unlimited but the core sketch to them that i find best to start development on are the following in my opinion:
#1 simple mechanics
#2 fun short gameplay cross the road like very simple and effective ludic loop effect / long captivating gameplay packed with things to do in the game, story line etc.
#3 must be multiplayer if you want to attract a user base, nobody today plays single player games anymore unless you are doing some massive game. (2d games can be massive as well don't think 3d here)
#4 simple graphics
#5 color balanced
#6 sound pack that matches the game and makes u feel cozy
if you follow this steps and don't overcomplicate things you can make cool games
as ideas you can get inspired from real life day by day objects or animals ex:
coffe, cocktail/juice/ice cream making or ants platformer you are an ant and have to collect bread crumbs to feed the hive. etc example are infinite anything you can think off. the problem most devs have is to keep it simple, everybody has this instinct on packing everything with all sorts of features and before you start you have a To-Do list that takes 5 years and everybody gives up in the end, because everybody wants it done by next week.