If after four films in the franchise you still aren't aware that these films have very little to do with the video games than there is no hope for you. Take the films for what they are. They are an alternative take on the universe we know from the video games and basically are an excuse to show off as many nonsensical matrixesque stunts and action scenes as possible. Preferably featuring super woman Milla Jovovich. That is either something you dig or don't. Retribution is no different. It is one action scene after another with only brief moments of plot or drama. Retribution also does a little fan service by throwing in some well known characters like Leon Kennedy, Ada Wong, Barry Burton and the return of Jill Valentine. BTW if you have the feeling that you missed the scene where Jill got captured and was brainwashed. Don't worry. All of this happened off screen. Some creatures from Resident Evil 5 also return. Plus you have some familiar faces from previous movies including Michelle Rodriguez. And like always she is extremely badass. Don't expect too much from the videogame characters since the focus of course is on Alice. One of the main reasons why Milla is in the center of everything is the fact that she is married to director/producer/writer Paul W.S. Anderson. Naturally this plays a huge role. Luckily this has worked out for everyone.
I know that the previous film had disappointed many people but I do think that Resident Evil: Retribution is a step up overall. But like with all of the films in the franchise it is recommended you shut of your brain when you watch the films in this franchise because it will make it easier to enjoy them as they are intended.
Both Resident Evil: Afterlife as Resident Evil: Retribution use elements (pretty randomly and without any logic) from Resident Evil 5 so I can really recommend playing that game: