I watched Red Tails the other day at a friends house.
The action scenes were very well done, the CGI was well done, the story it was based on was fascinating.
The acting was poor, the script was poor, and you could guess what was going to happen by all the stereotypes being acted out, and yet many of the cast were good actors (as could be seen in other series/films they'd been in*), so it could only be poor direction/script/production.
If it had been a decent script/direction I would guess going by the cast and action it would have been an easy 8
If I were to go by the script and direction, I'd probably give it a 3 - rather than a film based (loosely) on a true story it felt like I was watching Topgun 1945: The Ghetto years.
As it is, probably about a 6.
*They had Bubbles and another guy from the Wire, and Cuba Gooding Junior whose role seemed to be to stick a pipe in his mouth when happy, point with it from time to time, and take it out and look constipated when things were looking bad (seriously, that's about all he seemed to be there to do).