Via browser on desktop or mobile, you can play a nice selection of featured carts here: https://www.lexaloffle.com/bbs/?cat=7&carts_tab=1#sub=2&mode=carts&orderby=featured

Another list here:
https://nerdyteachers.com/PICO-8/Games/Top200/

I believe there are other ways to store and play the carts across other platforms, but you’ll need more help than I can give you on that stuff.