Who's the legal dude round here? I can't remember if it was the bear, or somebody else. Anyway, perhaps he'll back me up here, but I believe (and I'm not sure), that it's not possible to trademark a simple english word. This is why we often get films with the same title as previous films, and books with the same title also. If you make up a phrase like "Zuber Clan Warriorz" then that's defo trademarkable. If you just called your game "Balls" then, as far as I know, there's no way you can trade mark that.
I believe the problem only arises when someone releases a game that is very similar at the same time with the same name "Balls", at which point the 1st company might accuse the 2nd company of trying to muscle in on its market by replicating the product. Otherwise, I think the generic word can't be trademarked, and therefore so long as it's simple and the games are noticably different (preferably different genre), you're all good.
So to sum up:
If a game exists called "Mega Monkey Assault Deathoidz", it doesnt matter what genre your game is. You can't use that name. It'd be a blatently rip off of the trademark.
If an FPS game exists called "Blade", you can most likely release an RTS called "Blade" or a puzzle game, or racing game etc. but releasing an FPS game called "Blade" would put you in a potential lawsuit, although, as far as I'm aware, they couldn't actually trademark "Blade" itself - just the concept of an FPS called Blade.
That's my understanding anyways.
