Holy Crap! I can't believe I never mentioned or thought of that! Jubilee HAS been in the mansion longer than Rogue! Ideally, she would have been spotlighted just like Kitty, Pyro, and Iceman in the latter films... but they did cut her spotlight scene in X2. If that scene wasn't deleted, she'd most likely have been a bigger character in X3. It's a shame, really.
I'm not saying that Jubilee should have replaced Rogue in the final battle... since she hasn't been shown fighting at all in the films. I do think, however, that she needs to be showcased further in future X-Films moreso than any other character who hasn't had their chance to shine yet. Out of all the established movie characters, she is the most popular one to not have a power scene or battle yet. I can prove her popularity by Jubilee's number of votes in that 'favorite X-Man' voting that MSNBC had on their website.
She deserves to be in an X-Film... and I think that she's actually been stated by Avi Arad to be featured in the X-Kids film when it comes out in the future.