linear, one-dimensional - (of or in or along or relating to a line; involving a single dimension; "a linear measurement")

This is one of the 5 definitions of the word linear found in the dictionary. It seems to be a word that is thrown about a lot these days with regard to games, with Final Fantasy XIII being at the centre of recent arguments surrounding the subject. My personal opinion on the matter is that games that are considered to be linear are just as good as those that are not (this particularly applies to high quality FPS and 3rd Person shooters, but also many other games). 

My question to you is this:

Why do so many people think that a linear experience is a bad one?

I don't know. I suppose the comparison goes on FFXIII being more linear than its peers and previous games in the series (I wouldn't know), but I have no issue with linearity on a basic level. Some games are better at making you forget the linearity of the whole thing, and I think that a RPG like FFXIII where you're supposed to run around levelling up can have it more obvious than other games, like say Uncharted 2.

dont know either...

This is true, although I think in FFXIII they have done away with traditional levelling. In fact, I would say that "levelling up" has always been something that I disliked about RPG's. The easier it was to level up the more I tended to enjoy it.

well, the FFXIII linearity is really ... very linear

FFX was linear, but at least you were shown on a map where you are and there were towns and stuff .. FFXIII up until now (I'm 35h in) is just a straight path. I came across 1 "city" as well, but that didn't have any other meaning than advancing the main story .. there was nothing else to do there.

and the path itself mostly is a "highway" with monsters on it and stuff at the sides, which you can't interact with, pretty similar to what I played in the folklore demo

Movies are for linear experiences. I like my games as non-linear.

i'll explain in regards to FFXlll we are coming FFXll quite possibly the biggest JRPG world or last gen + every other JRPG or WRPG released this in current that all had huge worlds to roam, the fact that FF the king of JRPG's seems to offer less in certain area's than RPG's already out is weird. Then we start hearing about FFXlll possibly having towns in the past or FFVll remake possibly not being remade because SE doesn't what to model all the towns makes you wonder about FFXlll's development decisions. Plus western developers are leading and they create huge open worlds and have trained gamers to see open worlds as the standard.

But this issue is blown into overdrive, and im shocked ppl still haven't Xxcepted it yet.

There was a time in my life when hearing that a game was linear was a death sentence, because I relished the chance to immerse myself in a world, roam around, and find my own way. Over the years, though, a weird thing has happened to me. In extremely open games, I tend to become paralyzed with fear that I am making the wrong choices to the point that I find it difficult to play. Every time a conversation choice pops up in Heavy Rain, I have a miniature panic attack. It has actually worked out, because me panicking has led to some pretty funny and interesting results, but I find it legitimately emotionally taxing trying to make choices in video games, which is strange.

To me, being linear in this day and age is kind of like having graphics a step or two below the top level graphics of the gen. It doesn't mean your game is bad, or less involved, it just means that the developers have to do a little extra to make you feel like what you are doing still matters. Not an impossible goal, by any means, and there are many ways around it, just like good art direction/visual aesthetics can make up for less technically impressive graphics.

Because some people like options. People who like options shouldn't be playing Final Fantasy XIII. But they can still hate it for not being something they don't like.

There's a certain amount of freedom people expect in an RPG. If FF was an action adventure game there wouldn't be an issue.