i fucking suck at gungeon i guess. i've made it to the fourth level boss so far. i think i could make it if i kept playing, but it's not that fun going through the earlier levels, and taking the shortcuts leaves you weaker and makes the game even harder...
if you like top down shooter roguelites like isaac and gungeon you might enjoy nuclear throne as well.
spelunky is a platform roguelike that is a classic. i think there is even still a free version out there.
i can also recommend dungeon of the endless, which is somewhat of a hybrid of a roguelike, rpg, management and tower defense. really interesting and great artstyle and humor.
risk of rain is one of my favorite games ever, it's fucking awesome. it's not much of a looker, but once you get into it, it gets so good.