Which platform should I target for my new game? Do I need to make my own propriety gaming device? If I want it playable on a phone, do I need to make my own pho

Which platform should I target for my new game? Do I need to make my own propriety gaming device? If I want it playable on a phone, do I need to make my own phone? Or because Apple/google don't really make games, it's okay to release for iPhones and Android phones? Or should I just release on dominate platforms knowing there's some non-zero risk the platform owners might compete with me someday?