I know this doesn't answer what move is 'better' than Curse because that is entirely subjective.
However, there is no reason your G-Max Snorlax isn't able to learn Curse.
If you delete a move-slot from your G-Max Snorlax & breed a regular Snorlax with Curse aswell.
You can proceed to put them in the daycare together to transfer the egg-move curse. Genders don't matter, all that matters is that one snorlax has a free move-slot and the other has an eggmove to transfer.
All you need to do is ride up and down a few times and go & retrieve your G-Max Snorlax with Curse!