If you can find out why it is dying back and address that then it might be able to restore itself in a more uniform and pleasing manner. Probably has a fungal or bacterial blight that could be beaten back comparatively effortlessly by using a few well-timed, appropriate sprays each year. If, on the other hand it has cherry bark tortrix (look for holes and sawdust) likely you will have to get on that promptly and diligently or the tree will soon be history.