I'm just giving a suggestion anyway, no offense. unity and unreal engine (unreal development kit for the free version) can do such a great thing in my mind. To me, if you wanna look your game a bit cartoonish, you can use unity as a great partner of your development progress. or if your game wanna look a bit serious, use unreal engine instead (I give this opinion because I'm judging from the shader type of each game engine). you can use your assets (3d models, particles, maps, and etc), but not your code if you want to migrate it to game engine. you have to recode it in C#, Javascript or Boo if you're using unity, and unrealscript (if i'm not mistaken) for unreal engine.
PS: At the time when I gave that comment, I didn't think about getting the license from Universal studios. XD