When it all boils down to realism or feasibility, we reach a point where saving shouldn't be possible because it can't be done, crafting should take a fair bit longer for complicated things (grenades, anyone?), you've no real reason to find RAM on dead scientists, why are there underground science labs everywhere anyways, thing's shouldn't be unfinished because reality is pretty much gold master by now, and you know what, a zombie apocalypse is fairly unrealistic, y'know, where people rise up from the dead, or why you don't catch the zombie disease if it is a disease, so let's remove all that zombie nonsense, and quite simply, it's unrealistic to have a game about zombies without zombies, so let's just forgo the whole idea altogether, shall we?
For crying out loud, the entertainment is in the unrealistic or unorthodox- it boils down to escapism, a break from reality. You don't sit at a computer to play Office Peon 2009 or Super Traffic Conductor, do you?
I don't think it comes down to realism or feasibility. Realism and implementation, or how it is implemented aren't necessarily connect. There is a good way to implement facets of realism and bad ways of implementing them, in effect these are two very distinct things. Take the opposite, games wouldn't be playable even if they don't follow a particularly realistic approach if these facets are not well implemented. In short, how playable it is is not the direction of style or adherence to reality, but how the entities and rules in the game relate to each other.
Moreover, we look towards reality to gain an understanding of the world in these games. It wouldn't make much sense if most of the physical laws we take for granted in real life were absent or abandoned in the game. Likewise, we have a framework of understanding that we use from real life for games. We can accept that there are elements in the game that aren't native to this reality, but this doesn't mean that the rest of the game mustn't either. In fact, going down the route of going against all understanding of real life, however good it might be implemented, it will be very hard to make sense or and to actually have fun if it were the case.