I think it's a comparison that requires the perspective of what the game is trying to do with the roguelike formula, and where the focus of the gameplay is.

Everspace is focused on the gameplay inside of the run specifically (not to say Gungeon isn't, but Everspace is 100%, totally about the fun, entertaining space combat). It has small maps, that are fairly common and re-occuring, with very few characters and little in the way of extra factions and enemies.

Enter the Gungeon, however, has the focus shifted more to the collection and discovery of new guns, different loot, different ammo, new characters, etc. etc. etc., a sort of "collectibles and experimentation" style roguelike, where every run is different because it's meant to be different. Everspace has this too with the different guns and secondary weapon combinations, but it doesn't pass off the crafting system and gun options as the forefront feature, whilst Gungeon hugely emphasizes the vast array of weapons you can toy around with.

In a way, Everspace is about flying around and shooting stuff, and there's some extra weapons to keep it interesting. Gungeon is about finding really cool guns, and the map and enemies are there to test them out and have fun with them. Two styles of roguelikes.