I'd very much so prefer for you guys to develop whatever RPG idea you've no doubt had kicking around, as I'm sure that approach would yield the best results; far better to be engaged in a project which you wanted to create than have something thrust upon you by the community.
That said, if it happens to be something you're interested in, a modern urban fantasy RPG would be pretty rad. Think Angel, Dresden Files (the books), or Vampire the Masquerade: Bloodlines. I'm a huge fan of the genre, and I think it offers a ton of potential for dark, mature stories featuring deep characters in a setting that's far fresher than that of your typical fantasy RPG.
Isometric style would be awesome. As for combat, either TBS or pausable real-time suits me fine.