if I'm not mistaken in bomberman the movement is aligned, i.e. the player will only stop walking on multiplies of X pixels.
This is likely true. I've only ever played one bomberman game before (Mega Bomberman), but in that game x is several times smaller than the size of the blocks. Meaning the player won't necessarily be perfectly lined up with the blocks (or openings) when releasing the movement button.
I think in bomberman if you collide with a wall it also moves him a bit on the other axis to fit to the opening right?
Yeah, if I'm understanding you correctly, that's what I was getting at in my previous post. If a player is trying to move into an opening, but is slightly not lined up with the opening, it will first move the player in the other axis until lined up. As you mentioned, giving the player a "bounding circle" and allowing the circle to slide around the corners of a wall is one solution to that problem.
Anyways, I've realized these aren't really the problems cChaD is experiencing. He is more focused on getting basic collision responses working, so I won't derail this thread any longer