Why do movies get "nitpicked" so much?

I don't mean to disrupt the flow of opinions the make this world spin, but why is it that all those movies that are so bad to people seem good when I see it?I have my own opinion sure, but Terminator Salvation was watchable.So was Daredevil,Watchmen and so many others.I liked these movies because I thought they were good and I took them seriously, only to see them get pounded by critics(and fans)alike.
I really never see the whole problem with these movies that people seem to keep complaining about so much.I mean, it isn't like we are sitting through Barney or something.I just wish that just for once, movies could just go back to the way they were.Especially CBM's.The CBM's really need work but I feel that the majority of them were good.Movies like Blade Trinity and Daredevil were both enjoyable and watchable in my opinion.Yet they were pounded on quite frequently by people.
I know that they may not follow the source material directly,but Blade pretty much HAD no source material.If we took the Blade from Tomb of Dracula,we would get results like Matt Salinger from the first Captain America.Blade was a story and movie all its own.What did you expect?Daredevil was dark,gritty,and actually pretty realistic being about a superhero that was blind.What did you expect?
My point is not to anger anyone,but to just simply ask why and make people think for a second.I am not the one that worked my ass off to make those movies.I really never feel that I have a good right to judge because I took no part in helping with the story or movie at all.I don't think the critics did either.I just don't think it is fair when David Goyer(a HUGE comic-book fan)or Mark Steven Johnson(a HUGE Daredevil and Ghost Rider fan)should get pounded so much when I think they really did try with their films.(Ghost Rider did have bad acting, but was still somewhat good in my opinion.)
Just like with video game movies.They are all put down and insulted when some are actually really good.Honestly,Doom was able to have any story because it was a one-sided game,and was deep and enjoyable with good story and action.Prince of Persia was excellent and detailed and thoroughly well done I believe.Sometimes I think our biggest problem is the critics.Those(for half the majority)old people that never played a video game or read a comic book in their life,and don't even know the story that in which they are pounding so much.
You guys have your opinions and there is never anything wrong with that.Honestly though,some people just go off of what others say,even without seeing the movie in the first place.I just think that we as fans and critics, should lay off and take the time to see the good stories that these movies actually have.Because even if they were based directly off the source, people would still find ways to complain.
I think that we should just stop complaining so much and just enjoy these movies when deep down, half of those "bad" CBM's or video game movies really aren't as bad as they seem.Well, that is enough of my ranting and I just want to say to you all:

Good day peeps!
P.S.Feel free for debate below, but please I just ask that you be respectful.