Tron:Legacy is a very pretty movie, aesthetically pleasing with some excellent action sequences and solid turns from the actors involved.  The directing is admirable.

Fine.

With that out of the way, Tron: Legacy will ultimately be remembered as a failed movie.

Don't get me wrong.  It's not an overly bad movie.  The disappointing thing is that it's just not a particularly good one.  It's beautiful and aesthetically pleasing, but Legacy fails to deliver any meat on the bones of unique concepts. 

The concepts are generally interesting and unique:  The world of Tron is a gladiatorial Roman Empire blended with the Nazi Regime of World War II in its peak popularity.   Kevin Flynn (Jeff Bridges), the creator of this world channels Shakespeare's The Tempest and Shelley's Frankenstein as an exiled and stranded wizard afraid to face the monster he created, his mirror image from a younger time. Trapped with him is Quorra (Olivia Wilde), an interesting mix of Anne Frank and Prospero's daughter, Miranda.  They hide from the villain of the story, Clu, a Frankenstein's Monster/Hitler, a unique composite character trying to destroy his maker while still striving to do what his maker created him to do.

The script begins to show cracks when examining the protagonist Sam, Flynn's son.  Sam is a one-dimensional and poorly explored character as an abandoned son living a lonely and dangerous life.  There is no explanation for his actions in any way that makes sense.  

Sam's shortcomings could be overlooked, but it ultimately exposes the weakness of Legacy:  An unfocused plot where the secondary characters are more interesting than the protagonist.

Characters and elements are introduced without much effect or later impact.  Pretty much the entire first quarter of the story focused around the real world, where events had nearly zero impact on the rest of the story. Prolonged action sequences in the gladiator arena neither advanced plot or character development. 

Plot holes large enough to drive a truck through start appearing.  Why can Sam bleed in the digital world?  Why doesn't anyone think of backing up their disks?

The script ultimately fails through inconsistent or ineffective exploration of theme.  The movie grapples with the idea of perfection, premising that perfection can never be achieved, even if it can be visualized.  It is an ironically apt theme applying not only of the making of the movie, but of the expectations generated by the hype around it.

Finally, and most egregiously, there is a distinct lack of the titular (just because I like to say the word "titular") character, Tron.  Without being too spoilery, there was a fair amount of disappointment when Tron himself didn't make an appearance at the end of the movie.

To be honest, Tron:Legacy is a fanfilm with a budget and corporate backing, where the creators were able to break out their action figures and relive their childhood memories of the original film, but were unable to convincingly introduce anything new or relevant into the process.  But it did look pretty, and is an entertaining way to burn off a couple of hours.