>>724930969 (OP)
They are all Roguelike.
Roguelike is defined by having procedurally generated levels, equip and progression at every run, and if you die you start over from the beginning.
That's it, shit like the combat system, 2D vs 3D or level progression is just accessory and entirely irrelevant for belonging to the genre.
On the other hand, Metroidvanias key features include a sprawling map that you unlock bit by bit by backtracking as you get new equip and Dead Cells is definitely not that (hell, Dark Souls is more Metroidvania than Dead Cells).
Meanwhile a Bullet Hell is always intended to be a side scrolling game where you have to pilot your tiny hitbox (often much smaller than the sprite of the actual character) among a deluge of projectiles, and while Enter the Gungeon has some elements of that it has much more in common with TBOI than, say, Tohuho.