Yeah, this is well... I think you might be on to something with the Andrew Garfield thing, dude does look a lot more like spider-man more than he does Barry Allen.
I have a theory that Arrow worked so well partially because Arrow is a sort of minor character in the DC Universe, and then play around with that, where as Flash is in DC'S top characters, and deserves to have his own movie. I don't think TV special effects/TV budget is going to help out with the speed to look good at all as well.
Sorta brings me back to when they tried to do a Wonder Woman tv couple of years back that failed hard.
Spoiler for Wonder Woman:
Carlton Blues - Chicago Bulls - Manchester City FC