Because of a past as sort-of-toys (explained nicely here and here) important features of games are: How "fun" they are, replay value and how long they last. Reviews often take this into account and in turn this makes developers focus a lot on making a game "fun", "replayable" and "long lasting". I think this kind of thinking (which I am at times guilty of myself...) can seriously hurt a game. I think designers shall focus entirely on what kind of experience they want to deliver and make that come across as effectively as possible!
I have mentioned in a previous article how making combat fun can hurt the experience in a horror game, especially if scaring the player is the main goal. Instead of trying to make the combat as frightening as possible, combat is often added with little thought on how it affects the experience and much more focus on how "fun" it is. So instead of making a scary horror game a fun shooter is created (which is not always what is intended).
I recently finished playing the second Professor Layton game and while I enjoyed it quite a lot, it also had the same kind of problem. It is quite obvious that Professor Layton has been designed to last long and that a great deal of effort has been spent on this. The game has several side quests (collecting pieces for a camera, making a hamster loose weight, etc) and none of these are really connected to the game's story. There is also many puzzles in the game (150 of them) and because of this a lot of them are just different versions of the same type or just really boring and unimaginative. I think that the game could have been a better experience without these extra bits. For instance, with fewer puzzles more focus could have been put on making the puzzles that the player do encounter more varied and exciting. Instead, many of the better puzzles are put in as extras or part of side quests and a play through focusing on the story will miss out on them. If the goal with Layton has been to give the player an experience of being a puzzle solving detective, focusing on making the game last longer has definitely made it worse.
The last example I want to give is from the horror genre and concerns Dead Space: Extraction (which Jens have been playing lately), an on-rails-shooter for the Wii. The game tries hard to immerse the player and create a frightening experience, but makes a serious error. To give the game more replay value and "fun", the player has to hunt for bonus boxes, some appearing for a very short period. This happens all of the time and has several negative effects. Cut-scenes becomes treasure hunting sections and instead fearing what might lurk behind the next corner the player focuses on catching goodies. Collecting these bonuses is of course optional, but having extra ammo has a great impact on the gameplay and bonuses also include interesting story material (in the form of audio logs). Worst of all, it makes the on-rails aspect a lot more noticeable. If the player just barely misses a bonus because of a change in view, the player will want the character to look back at the previous area. This creates a sort of struggle between player and protagonist, seriously reducing immersion! I think this a very clear example of how focusing on the wrong features creates a less compelling experience.
Of course games should not take too little time to complete or be absent of fitting replaybility. However, I think that it is very wrong when it detracts from the wanted experience. Making sure the game is fun, replayable and long lasting should not be a design goal in itself, but something that is added if possible.