I think honestly you'd almost have to try to make worse movies than Ep. 1 and 2 at least.
Those movies have literally *nothing* going for them outside of lightsaber battles.
The acting is terrible, the story/plot is weak, the characters are dull, the editing meanders all over the place, the "love story" is hilariously awful, the cinematography is dull and static, the "humor" is a trainwreck, and dialogue/writing is terrible.
Well I guess John Williams' soundtrack for both are good, but that's about it.
If the only thing JJ gets right is better characters/dialogue/acting combined with more tension in the plot, he should surpass the sequels easily. The special effects stuff is going to take care of itself because the effects we have today are so much better than the OT, so that's not the issue. Once people see a proper Star Wars movie again with those solid storytelling elements back in place ... IMO the prequels will look that much worse, because they won't be able to hide behind the more modern effects/production value (which is really all they have going for them).
It'll be like a good looking girl who has a terrible personality suddenly put next to an equally or better looking girl with 10x better personality, suddenly you realize how terrible that first girl was.