At the time Tron had no RPG, Dune was out of print and out of my price range, and Dredd was represented by an old Games Workshop game I disliked intensely, and a Mongoose version that I rejected because of the high cost of entry (you had to buy Traveller and their Dredd publication, and I just noted the Dredd book isn't for sale on DriveThru anymore).
What I did was to fall back on the FATE system. FATE is generic and generic systems usually lack all the flavour and weighting of odds to make a session feel like you are really in the universe of the IP you are playing. BUT! Fate overcame that problem for me. In each case I produced a bunch of IP-based skills and a small collection of IP-based feats and tags. I also produced themed character sheets with art that set the scene.
The sessions were a success, and I think that's because the "taste" or "feel" of the world was modelled in the changes I'd applied to the core FATE system through skills sheets, and tags. I would generally suggest that you should go with a franchises actual rules if available as usually (we always hope) the author has put the flavour into the game mechanisms, but a generic system can work as a fall back.