i don't know because catching some pokemon that are almost hard to capture is the cheating part but some of the other stuff is impossible, so it could help, i'm also asking because i'm a fan of nintendo and nintendo says it is just plain cheating.
I think an action replay is definitely cheating because it allows you to do things that aren't intended for you to do. Ex. Walking through walls or trees. Another way it is cheating is using it for unlimited masterballs and this allows you to catch any Pokemon without trying and to me that is cheating