People say a movie like Twilight is review-proof. Well, I`d assume a Resident Evil movie was as well, and I almost didn't bother. Then I got to thinking, Extinction was pretty bad. Bad to the point where some people may have just say "Forget it, I'm not going to bother." And I think that'd be a terrible shame. Afterlife is a great Resident Evil movie. First thing's first. This was filmed in THREE DEEEEEEEE. Whoo hoo. Since it was actually filmed in 3D, rather than being a conversion, it doesn't suffer from murkiness or fuzziness like the quick-'n-dirty conversions can. That said, 3D is still not a terribly great gimmick in general, and I find the glasses really annoying. Any brightly lit scene has a tendency to look very, very green-screened, and it doesn't add much to the movie. Then again, 3D doesn't add much to any movie. See it in 2D if you have the option (I didn't), or wait for home video if you've got a decent set-up at home. Apart from the green-screen look, the effects are all top-notch, and really deserve to be seen clearly.
I'm going to a) assume that you've not seen trailers for the movie (I hadn't, somehow, before seeing the movie), and b) are at least passingly familiar with the the previous movies, and the games, or at least RE5. At the very least, you really need to have seen the third movie, or you'll be completely lost, and to get the most out of it, having played/watched someone else play RE5 is a good idea. Of course, being able to understand those carries their own requirements, but such is the burden of the world of Umbrella.
Alice and Claire Redfield are back, but Claire gets amnesia in an attempt to through some tension in to the movie when her brother Chris is found. But the most important thing is it deals with Alice's clones and superpowers in the first ten minutes of the movie. To put your mind at ease, I'll tell you flat out, Wesker blows up all the clones, and removes Alice's powers. From there, the basics of the plot is "find safe haven."
As I said before, the effects in this movie are good. Damn good. It steals zombies from RE5, which are canonically different from T-Virus zombies in the games, and have tentacles coming out their mouth, but no reason for this variation is ever given in the movie. Ever heard of the trope "A wizard did it"? Well, just assume Umbrella did it. Why? Uhhh... Look at the pretty effects! Woo! Shiny sparkly! *waggles fingers* Yeah. Also, in a nice twist from the previous movies, Chris isn't completely useless, and neither is Claire. Game characters not being useless in the movie? THE DEVIL YOU SAY?! No Jill Valentine in the movie, though, despite the liberal borrowing from RE5. There is a stinger after the first bit of credits, showing that we're pretty much staring down the barrel of a fifth movie. Nice little speech, and confusing as hell if you don't make the connection of "Oh right, in RE5, they changed that."
I really don't think I can state this enough: this movie undoes a lot of the damage from the third movie, and borrows liberally from RE5. If you liked RE5 and hated Extinction, you should really enjoy this movie. Take a chance. Enjoy Resident Evil again. Continually moronic plot and all.