Romero's draft that's all over the net was also written in 1998. How many games have released since then? The script might not have been the best thing he's written but if you looked at the first two RE games as his source material can you really blame the man? Even RE enthusiasts like yours truly know the original game script has some pretty silly dialogue.
As far as the movies are concerned the only reason I see them as successful is a mixture of the gaming community alongside people who do just want to see a popcorn flick. It's pure trash, but entertaining enough to find an audience out there. I like zombies and watching people fight evil corporations. Whether the movie is bad or not doesn't reflect going out to the movies with friends and having fun with it or at how bad it is.
We've seen lots of things that deviate and still end up successful. The Dexter TV series. Kubrick's take on the Shining being a few of my favorites. What they leave out from the source material they make up for in other areas be it good writing or memorable characters.
When I saw the first RE movie I was entertained but couldn't remember a single character's name in that flick. They were generic nameless characters that died off and "that chick from the 5th element".
Now a days the more game elements they toss in the easier it is to pick apart. The loveable and supportive comrade Nicholai.
Carlos "I spelled his last name wrong" Olivera.
Some girl in the back named Jill or something.
And then as far as movie characters go we've got Mike Epps.
Not Jason Issacs...
And Sarah Conner.
All these "interesting" characters that needed to be in the movie over legitimate game characters. I wasn't expecting Jill to push a crate for 90 minutes. But you got to expect the characters you grew up with in some form of plot reminiscent of the earlier games.