agree

A railbox: a box of rails to build your own railroad...wait, isn't that like the Railroad Tycoon games?

Damn you who said railroad tycoon before I could crack a poor joke with it.
But topic:
It really depends. Sometimes it's just fun railroad my through hordes of enemies in a pipe like Gears of War or follow the "movie"like story in Heavy Rain.
Other times I just want steal that damn jet figher and go and bomb some oil wells in Just Cause 2.
It just depends on my mood which kind of entertainment I want at the moment.
And it wasn't my fault what happened in Mexico Gulf...

Wait, where does FFXII fit in here?

Bah... Me too, I was just about to come in with a Railroad Tycoon one... :)

Just like Just Cause 2. And in both the destruction gets a little too repetitive when you destroyed bazillion whatever you have to destroy. Luckily in both games you can just go and cause some chaos when things get too dull.

I'd say it's somewhere in the middle. In the beginning it is little bit railroady but open up. But not like GTAs or other "real" sandboxes. Best FF game still.

Both Sandbox and Railroad have their place, but I think the best game is one with a bit of both.
To elaborate a bit:
I really enjoy the sandbox environment of Mount & Blade - you can decide what you want to do, then go and do it.
On the other hand, I also enjoy 'on rails' FPS games (e.g. Jedi Knight 2).
Best of all, I think, are decent RPGs like the Witcher or the Baldur's Gate games which have a definite path to follow, but also allow you to wander around on side quests.

No problem, yours phrase was a good one. ;)

I don't think one is better than the other, it's more a matter of whether the functions of the game design fit the game's intended effect.
It depends on what the game intends to achieve. If the game wants to be strongly driven by its narrative, then it's usually better if it's driven in a linear way to have an appropriate story arc, so railroads work best.
If the game wants to make me feel like I live in the world, that I have freedom and choice in the role I play, and that my decisions and actions matter, or promote exploration, then the sandbox is the way to go.

I tend to prefer a sandbox environment, but with a fairly structured story and soft barriers (e.g. strong enemies) to open the world up slowly as the story progresses rather than being able to safely run anywhere from the start. For example I'd consider the Gothic series (sans Gothic 3) to be a good example of this kind of game design.