Game Creation software

I'm not entirely sure if this is the appropriate thread to post this in so if a Mod could help me out that'd be fantastic. 

I'm trying to create a 3d FPS/flight simulator game however I'm not exactly sure what software would be best to do this. I've used the blender game engine before but it seems fairly limited in terms of what can be done. Well, that and I want this to look a little more professional. As this will be my first attempt simplest would be best but I'm happy to try new things and learn new skills. I've already modeled most of the level meshes and am currently working on NPC and weapon meshes so modeling/texturing isn't necessarily an issue. 

I've rendered a few of the level models and posted pictures to my DA so if you're curious they can be found at: 
Thanks in advance for any advice or tips you can give guys.