I think if someone can write a decent article about a hack (like, say, if it has a reasonable amount of changes, or some history behind it like 1990 Tank, or it was really popular, or its interesting for some other reason), then it can have one. I don't particularly want this wiki to end up like Wikipedia where perfectly good articles get deleted because someone decides it's not notable enough.
but if it's just a title/main character sprite hack where you can't say much more about it than one sentence and a screenshot, it could probably go in an overview article along with similar hacks. so we could have an article for Twin Eagles hacks (except Sonic 4), one for Inventor hacks, one for those Pokemon "colour" platformers, etc.