I'm thinking of making a game with a "3D" map. By 3d, I mean that the map will have 3 axis, however it will be a fixed isometric view, without smooth rotation, probably just 4 different 90degree views. So based on that what should I be looking at doing, 3D or 2D? (is this what they call 2.5D?).
If you don't have a lot of experience I'd suggest you go with 2D and "fake" the 3D look by pushing the height together (to get the isometric look). You then don't have to worry about 3D models and all the other annoying things that come with 3D
If you are already experienced with 3D/Java then for looks and speed it's nicer to go with OpenGL.
Keep in mind that with your "turning" requirement you'll end up making 4 pictures of everything if you go with 2D and just one (although possibly a lot more complex one) if you go with 3D.