I was 4 when the original Tron came out. We had it illegally copied to VHS, and I have probably watched it more than 20 times. I saw Legacy in the theaters, and again a couple times since. I thought Legacy was visually fun, but had a scattered story with a bunch of half-developed ideas (Clu's planned conquest of the physical world, the whole iso thing, Flynn's wasteland area.) None of these things were actually consequential in the film - introduced and then discarded. Nonetheless, I enjoyed it for what it was.
Ares was awesome. It was a better sequel to Tron than Legacy was. It didn't have some deep, emotionally compelling story, but neither did the first two films. These are films about computer programs as little people inside computer machines that wear funny glowy armor and fight with glowy projectiles, light up motorcycles, tanks, and whatever the hell recognizers are. Ares was that, and didn't try to pretend to be something else. The soundtrack was great, the nostalgia and tie-ins to the original were perfect - neither over nor underdone. And it was refreshing that there didn't have to be a dumb human/program love story. I really thought they were going to ruin it at the end with Ares and Eve smooching, and was glad they didn't. Go see it, have fun, and ignore the naysayers who think Legacy is the pinnacle of cinematic art.