1. It is boring and clichéd even though it obviously attempts to not be
Quorra doesn't sleep with Sam and they all talk like it's a cheesy 80s movie, and not in a nostalgic cool kinda way, man.
2. The plot makes no sense
Clu is an asshole and totally throws off Flynn's Zen, why is he such a buzzkill, dudebro?
In the middle of the movie when Sam meets Kevin Flynn at his hideout he explains what happened to the Grid:
That he created the program Clu (an apparent clone of himself) to create "the perfect world". Then he talks all about the ISO's. But this is where it gets tricky:
Flynn then explains that Clu staged a coup of the Grid and attacks Flynn and Tron.
But why? Why would a program decide to take over and turn against its creator? This part of the story seems to be the most important, and yet it only gets a line or maybe two. They really should have given this aspect of the story more depth and elaboration.
"What about the ISO's?" you might ask.
NOTE: If you don't care about petty details, skip the next two paragraphs, bro dude.
Before Clu attacks Flynn he asks him: "Am I still to create the perfect system?" (note: not world but system). But then we see his orange-suited helpers suddenly appear out of nowhere while Flynn explains that it was a coup, right? This proves that he had planned this beforehand, and had already decided on going against his master.
So the fact that he was programmed to create the perfect world doesn't seem to mean anything, seeing as he now wants power and to take over the world and be all evil and torture people by forcing them to play games etc.
Then afterwards Flynn explains that Clu saw ISO's as an imperfection (why?) and destroyed them (after he took over, of course). Shouldn't they have reversed the two? What is the perfect world/system? And why would Clu consider the most intelligent life form with endless possibilities in the system an imperfection when Flynn said they had been looking for intelligence "higher than our own" for centuries? Couldn't Clu have used them? How do they expect us to believe in this shit if you don't actually explain how they didn't live up to CLUs definition of perfection. Flynn only says they didn't have a work order.
The only apparent conflict is that Flynn took an interest in the ISO's, but Clu wanted to destroy them (how do you destroy something that comes out of nowhere anyways?). It's not like he couldn't have just eliminated them either without turning on Flynn like a crybaby for "betraying" him. Maybe Flynn is just a terrible programmer, although that is beneath the surface like most of the important plot points.
SPOILERS AHEAD (heavy stuff):
Then later in the movie when Clu and Flynn confront each other by the portal, Clu claims he did everything Flynn ever asked. Establishing the fact that he still took orders from Flynn. He also refers to a "plan" and taking the system to its "maximum potential". Yet claim they worked "together" and that Flynn "broke" the "promise" to create the perfect world together. If Flynn is the one who "betrayed" Clu, doesn't that contradict Clu staging a coup all by himself and deciding to cut Flynn out of the loop? A forced explanation of how perfection is unobtainable ensues, which makes you cringe. This is really as shallow as storytelling gets. It's the Star Wars prequels all over again: referring to a bunch of unexplained shit that the viewer is supposed to care about, but don't because we're not shown any of it. So it's really just a bunch of empty talk. Maybe if they had shown the "betrayal" and not just CLU punching Tron in the face it would actually have been believable. But they didn't.
Another part of Tron which doesn't make any sense also has to do with another characters motives. Tron - the program created by Flynn's partner is reprogrammed, right (even though they never explain that)? Because at the end of the movie he suddenly decides to attack Clu in order to help Sam, Kevin and Quorra get to the portal. This simply doesn't make any sense within the context of the movie.
3. The characters are terrible
Play air guitar with your cane and you automatically become the best traitor ever. Right? Right.
The characters that inhabit the Grid are so lifeless and dull that you'd almost think that is point of the whole bio-digital jazz (man). First of all Sam Flynn isn't a bad character, he's your standard I-don't-know-what-the-hell-is-going-on-in-this-place character and all that comes with it. But then we get to Kevin Flynn, whos character is so boring and uninteresting that it almost ruins the entire movie. First of all he talks like a hippie (throwbacks to Big Lebowski anyone?). His meeting with Sam is incredibly unenthusiastic. And I don't mind the usual "I'm so glad to see you but this is a bad time", but with Flynn this is so overdone and terribly executed that it is awkward and sleep-inducing. And don't try to justify it as "that's the point", this isn't an art film, this is just inappropriately, painfully boring to watch. And without a single line of dialogue to inspire who can endure it? It get slightly better when he explains how Clu took control over the Grid though (even though the movie is pretty much ruined at this point).
4. Shitty fanbase
I don't need to see a shitty movie twice to know that it's shit. Screw you, Tron nerds.
Try to question the logical fallacies of the plot and people will say that you didn't pay attention and should therefore see it again. I did pay attention, YOU should see it again, because it seems you missed how bad it really was. Your movie sucks, deal with it nerds.
It really isn't my fault that all of the subtleties of the plot get lost in the hollow dialogue of the terrible characters. You don't go around analyzing stupid action heroes in Transformers do you? Exactly. Most of this shit makes sense to you because you read the backstory from the comics or wherever; shit that isn't explained in the movie.
The way I understand it, the movie was supposed to be much longer (2h50m) but they had to cut/dumb it down for the target audience (because, really? Who's gonna sit through a 3-hour movie about nerds?). The director/screenwriters are still shit though. Even though Disney sucks. They suck hard. Fucking Disney, dude, man and their Cars. Fucking Cars 2, goddamn stupid talking cars gonna ruin everything. Shit, fuck.
So here's hoping for an extended version with extended backstory and scenes which actually explains some shit and takes advantage of the interesting concept/plot.
And to round it off, here's four...
Reasons why it doesn't suck as hard it could have:
1. Great soundtrack
2. Interesting concept
3. First third of the movie is actually good/interesting
4. Slightly impressive visuals