I've said it before but the story just wasn't good. the soundtrack was meh, I mean it's not even a good NIN album and if were to stand on it's own it would likely be considered the worst NIN album.

All they had to do, story wise, was just follow up Legacy. That's it. They could have just made it a redemption story for Tron who would not only be again "fighting for the user" but also for the ISOs. Have Sam and Quorra go back to the grid to finally save Flynn, help Tron, and bring the ISOs to the real world or simply make the grid a peaceful place for the ISOs and have Tron become the grids leader. whatever. that's all they had to do. Hell they could have had it mirror god damn Steve Jobs and his return to Apple because THAT's what it felt like they were setting up in Legacy. I know that's silly but that was the path they were heading down. They didn't need Dillinger and all that.

the thing that made Tron and it's various spinoffs work is that at the end of the day there's a user that is hailed as a sort of God that tries to fix things on the grid. There is no User in Ares. hell there's no Tron in Ares.