I haven't played many Soni games after the first couple and my knowledge of storylines are virtually non-existent, but my understanding with Tails is that Colleen O'Shaugnessey voiced Tails in many of the more recent Sonic videogames, but I wouldn't say there's a real sense of gender. The main plot I'll put in spoilers
Not knowing much storylines, and after the whole fiasco of them having to redesign Sonic to look more like a little hedgehog and not that horrific long-legged monster they had originally planned, I wasn't sure what to expect with the first film, but I gotta say, they're both really good. I can't say if they're faithful to the games or cartoons, because I never watched any of the cartoons, but as movies, they hold up and my kids liked the first enough to want to see the second as soon as it came out. And I kind of liked the bigger feel of the second more.
But they're both worth seeing.