Nickompoop said:
There have been good, linear games made: the Half Life series, Portal (I assume Portal 2 fits this too, but I haven't played it yet), the Left 4 Dead games, Bioshock, Metroid Prime, and Super Mario Bros. (all of them) leap to mind. These are all excellent games; hell, Half Life 2 is commonly considered the greatest game ever made. Every game in this list brutally linear.
Metroid Prime is linear? I have to disagree on that one for a variety of reasons, though admittedly there is a semi-defined "path" you're expected to take in the game. The thing is that path overlaps with itself numerous times, and the series is very well-known for it's backtracking (exploring previously completed areas for upgrades & items). Sequence-breaking [http://tvtropes.org/pmwiki/pmwiki.php/Main/SequenceBreaking] is a common practice for experienced players of the franchise, which allows the player (using a minor glitch or two) to go around the expected path and acquire some key items much earlier than intended. Anyhow, the key point is that
Metroid (referring to the series as a whole) is traditionally considered non-linear.
Back to the main question, linearity isn't objectively bad... but it does create some problems. The issue primarily arises when a game is
obviously linear, especially when things start to get repetitive.
Ultimately, almost all players want some variety in their gameplay. If you're going to make a linear game, you can't have it consist of the same thing over and over again; things have to be mixed up a bit or else the player is just going to get bored of repeating the same task without deviation. In a non-linear game, the player is given the option to deviate from the main course at any time they want (how far they can get may be limited at first, but the game world opens up more and more as they progress). Sand-box games can be described as being primarily or entirely composed of these deviations, and quite often the entire point is for the player to just do as they please.
So yeah, you could say linearity is inherently bad for a game... but
feeling linear is definitely a negative aspect for any game. Because games are interactive, players want choice (which leads directly to variety). If a game is going to be linear, variety has to be incorporated into the level design. In a non-linear or sand-box game, players have the option to make their own variety if need be (though overly repetitive level design and/or not enough variety is the possible activities can still be an issue).