Since we got votes for all of them, I'll add more on each:
Resident Evil: Atonement = As the course of the story will focus on an Umbrella Corp faction, your characters could be scientists, technicians, soldiers, and intelligence agents of the company, but you are not restricted to Umbrella Corp. You can play other soldiers, civilians, and scientists for protagonists. Just no S.T.A.R.S. or other Umbrella Corp (especially Albert Wesker, if using FC's) as allies. The heroes pretty much established the whole of the company as enemies, and other Umbrella Corp factions would see you as defectors, traitors, and competition.
Talespin = No story to work on as of yet. You can make not only characters, but also planes from the show and from real life in the 1940's (jets are limited). One debate I'd mention would be the idea of humans in the story. I brought this up that despite the fact that all the characters in the series were non-human, there were some indications of humans, such as wanted posters and fairy tales with humans in them.
The Rift = The story basically starts when the Northern Lights appear all over the world in different times, and then a dark red crack appears in the sky and emits a wave of energy over the regions. When the heroes (& villains) come to, they find themselves in a cold dark mountainous wilderness almost like Balto's world outside Nome. You can use characters from this list, and we can add more in discussions:
Balto
All Dogs Go to Heaven
Rock-a-Doodle
Thumbelina
We're Back
The Land Before Time
Banjo & Krazy Legs
The Secret of NIMH
Ferngully: The Last Rainforest
An American Tail
Once Upon A Forest
The Pagemaster
For the OC Rift Fey, think of them as 4-winged Tinker Bell-like fairies. They are most likely from within the "crack", and they cannot survive long outside their world. However, they have special powers to hurt, heal, or help those around them, and to protect themselves.
Star Wars: Fleet Wars = Nothing to add much other than profiles, which I can work on after we get enough votes to put this in a new thread.
G.I.Joe: Wrath of the Scorpion = We can do FC's, depending what base we put this story on, from three main factions: UNSO, Cobra (either Pharmaceuticals, Corps, or other), and Scorpion Clan. Weapons and equipment we start out with will be modern and near-future technology.