+1 for GameEngine and associated editor improvements.
A competitor to Unity3D would be nice.
As a complete suite Blender and BGE beats Unity3D. You have everything you need in just one program.
Unity3D provides some nice point’n’click things and more easier to use shiny stuff and an improved engine.
By improving BGE more people would try it. With more people around, more stuff is needed, also on the editor side.
But there would also be people that would provide plugins and therefore make Blender and BGE better.
Just some improvements that are floating through my mind:
→ easy (especially on the documentation part) usage of dynamic libraries and low-level engine improvements written in other languages (particularly C++)
→ easy usage of non-python scripts/modules, like C++, Java, C#, … (e.g. create a dyn. lib. and use it via C+±Script-/Module-Controller)
→ OpenGL 3+4 support
→ integration of a high-level shading language like surface-shaders from Unity3D or OpenShadingLanguage
→ code-completion in editor (e.g. bge python and shader stuff)
→ independent game window so you can tweak stuff in Blender
→ ability to tweak variables while game is running
→ shop integration for plugins and assets
→ integration of a version control system, version controlable blend-files
→ more detailed profiling
→ better lighting (I know it’s being worked on in candy/harmony)
→ ability to export/deploy to different platforms and not just to yourself
→ better/easier system it insert and keep track of project-assets and prefabs/linked objects (also those that are not in the blend file but in project path)
→ hardware particle system (I heard that someone is also working on that)
→ special game screen layouts
→ game logic sets ( putting different SCAs in a set/group, loading and saving those, adding sets on different objects, having different sets on an object, e.g. loading a first person set on your main-char-object)
→ same 3D-view when I switch screen layouts
→ easy system to do shadow- and lightmapping for e.g. all statics objects in scene
→ easy/simple GUI system [seen that around here]
→ easy/simple multiplayer system (if not integrated then e.g. a simple system to talk to e.g. RakNet) [yeah, here is already flying something around]
→ (deployment of an HTML5 version)
Just looking at the differences between Unity3D Pro and Standard I must say that BGE already has lots of the features that are just provided by Unity3D Pro.
Better publicity of BGE would be nice.
On one side for the game-devs so that they know that there is more then Unity3D.
On the other side for e.g. universities so they and their soon graduators know that they could do some awesome research and improvement for BGE. E.g. providing thesis topics like DICE: http://publications.dice.se/publications.asp?show_category=yes&which_category=Thesis
On my university the game devs just know of UDK and Unity3D. Some also have heard something about CryEngine. Still, most teams now use Unity3D. Blender they know exists as some hobbist 3D modelling thing, but not as also having a quite good game engine.
And as our computer science curses are cooperating with those game dev teams we also do a lot of coding for and in Unity3D.
Seeing them using free software would be nice. But even better it would be when we all would go BGE and that way good games would be created with it AND our cs-dudes also would be able to improve BGE and provide new plugins and scripts.
I also think that for now Unity3D is just a bit better and easier to use. So I won’t recommend to them changing now.
But with all those changes that are coming to BGE there might be a good start promoting BGE out into the masses.