Just because a majority of people suck at it doesn't mean we shouldn't expect it, or that writers shouldn't try and achieve it. In fact, since it is so hard to do then I'd say it's worth going for more than a literal translation. However because it takes, y'know, intelligence and actual writing skill, and because most of the bankroll usually goes into getting the license in the first place, and because the producing staff only cares about getting money otherwise they wouldn't give two shits, and because adaptation writers aren't that skilled to begin with most people get angry when a particular product doesn't translate well.
It's sad that most fans have a predisposition that anything that isn't as close to the original will automatically suck, but I guess that's the ditch creators have dug themselves in. Although a ditch lined with gold.
But my point still stands, ideally a cross-platform creation should have a reason as to why it's being transferred to another medium. Perhaps there's an aspect to the setting or theme that would be better suited to one medium over another. If there's something important we can say about Rorschach's character that can only be done in a video game perspective and enhances the story then ok, if there's something about movie editing and it's sense of time and place that can start a dialogue about American history and philosophy then we should give it the go ahead.
Seriously, aside from one guy I know who's staunchly anti-comic and pro-movie/games who didn't read the original book cause he's a lazy nigger an asshat, everyone else who's looking forward to the movie, and easily the largest percentage of ticketsales will be fans of the original comic. I will say that it does have a chance to breakthrough and reach a wider audience (like what happened with 300), and 300 also has cultural relevancy if you watch it as a commentary on the war in the middle-east (though a very weak one.)
I guess Watchmen might also have some kind of deeper meaning to what's happening now, but if it does it feels extremely weak. Don't get me wrong, I think Watchmen's justification for being made as a movie is stronger than say, Spidey 3, but in the end it was put into production because WB finally feels they have a director who can make comic adaptations and not piss fans off, who are going to see the movie cause it's Watchmen... As a movie. It's the same reason Dragonball is being made, but luckily Watchmen doesn't look like shit.
Err, guess I'm digressing hardcore. Basically, just cause it's hard to make something worthwhile doesn't mean we shouldn't aim for it.