I understand what you're saying but with a game like Dead Space - no. You're playing it wrong. lol
The point of the game is to not run. It's to face your fears and strategically fight monsters. If anyone is beating the game in 4-6 hours, then you're not fighting but instead running and/or just spamming same weapons over and over again because they "work". Therefore - you're cheating yourself out of $60 and claiming the game is "too short for you." Yet, you haven't even used 3/4 of the weapons or kill methods the game has to offer you. Nor do you have anything to say for the incredible story you probably passed up. Getting the "gist" of a game like Dead Space isn't justifiable for you to say the "game is too short".
Some games, like say Halo, are short merely because sometimes they're devised for you to run through them. Halo, you're supposed to be super soldiers or Rambo in space. That is the point of it whether you want to believe that or not. You're not really supposed to walk through Halo levels unless... you want to and that's your gameplay style.
Dead Space is not. It's the exact opposite and it requires you to take your time.
The game doesn't force you to walk through it all the time though. Not because it wants you to have the choice of running through it - but if the game had "quarantine" lock downs or required hacking minigames every other room that forces you to face your fears then no one would like the game.
There is an interview here I have in the limited edition game guide (buy them merely for aesthetics and cool stuff, like the 100 pages they have in here) that has the art director saying that he wishes that people would take their time in the game to see all the art that goes into the game to create this atmosphere. He knows that no one is going to simply walk through the game and stop every couple of steps to admire small details but he doesn't want people running through the game as if on a time limit.
He also mentions it,"Probably not [in response to the question about people appreciating alot of the work] but this can be a virtue in itself because people love to feel like there's more going on than they can take in easily, that there are layers of storytelling and detail for them to investigate if they want..."
Anyone who rushes through the game and ignores those layers of storytelling and detail cannot sit here and legitimately say that the game is too short. It's not fair, plain and simple, and anyone who wants to sit and complain about the game not being short needs to take a trip through the incredible game again.
Sandbox games and RPGs are seriously hard to even be considered in comparison to alot of the games in question here. You just can't do it. Those games are designed with length and variation as goals/requirements rather than actual additional bonuses if need be.
A game like Dead Space doesn't need to be stretched out further than it has in it's story arc. Dead Space 1 did alot of BS crap to string the player along. That was the number one problem of the game: you just went from problem to problem to problem as if the story writers were just coming up with multiple ways to make Isaac have to do miscellanous crap just so the game didnt have to end.
Dead Space 2 fixes specifically and actually gives reason to alot of the problems you have to do. And honestly, it's just right. Not a problem more or less that you have to fix out of the comfort range. The devs could've tacked on another 2 or 3 hours worth of gameplay that simply strung the player along but that wouldn't have been necessary.
That and they give you plenty of reason to play through it again.