I am starting to develop a space empire building game. I have made a rough prototype in Python, but now I am redoing it in C++. But I can't deside wether to do a 3D map or 2D map.

I envision that the 3D map was something like in this video. Skip to about 00:10 to see the 3D star map.

I don't think that implementing it would be any more difficult than implementing 2D map. Only thing that would change, is that every object has additional coordinate. I don't plan on having too many objects cluttering the space anyways. Dots for stars and triangles for fleets. A fairly minimalistic game, where I try to keep everything at macro level. Implementing map overlays, on the other hand, would require an innovative approach.

I am worried that a 3D map would be too confusing.

Help me decide, please.

2D, definitely.

Any reason why?

Navigating with a 3D star map gets very complicated.

I favour a 2.5D approach. At maximum zoom have a 2D map, once you get down to a dozen or so star systems, go to a 2.5D system.

Something like an isometric view would work

2D, definitely.

Any reason why?

Can you name one good game with 3D star map (excluding shooters of course)? Or popular one? Or playable one? Just one, because I never, ever found any. I still remember the terrifying 3D star maps of Imperium (EA)... It was horror

Planetary Annihalation is a pretty sweet game, that has 3D maps. Battles on planets take place on a 3D sphere and inter-planetary action is perfectly represented aswell.

Homeworld RTS was supposed to be a 3D game - or was it wnother space RTS, I don't remember.

Starshatter: The Gathering Storm carrier-command ship command mode featured a 3D map to assign missions for the fleet.

Those all are from the memory, I might be totally wrong about them having a 3D map though.

Ask yourself what going 3D will add to the game.

Negatives to 3D are that it is harder to visualize, and represents a vastly more complex world to work with.

Positives are that it represents a vastly more complex world to work with. (You have to pick if that is actually a positive or negative impact on your game.)

Personally I like 3D when it comes to something that I explore, but control relatively few things in. 3D strategy games become far more complex and aren't always actually an improvement over similar designs done in 2D fields.

Now that I think about it, 3D map would make my game little bit more enjoyable perhaps. It features as few micro-magamement stuff as possible. Only things that a player is going to look at, are stars and the lines between them. And the only things a player can interact with, are stars and fleets orbiting a star. And fleets also, can only fly from star to another star. There are no cliche starlanes though(although I might implement a possiblity to create a starlane at a high price.

Since my game is stripped down macro-management game, a more complex world to work with could compensate for the general emptyness.

Well since the current scientific theories suggest the universe is more or less flat I'd make it 2D.

Also 2D is far more easier to work with and visualize for the player. For one thing you don't have to start rotating the star map around to find which is the closest planet to send your fleet to.

Milky will appears flat if we look at all the billions of stars from a far away. My game is more about looking at 300 - 1000 stars at a time. Like watching at a cluster or a section of one of the Milky Way's arms.

Technical problems can be easily solved with map overlays. For your concern, there could be a proximity mapmode. You activate it and select a star as the target. Then all stars will be overexxagerately bigger the more closer they are to the target star.

I'm with Acharis. It's okay to have the map rendered in 3D, but only on a mostly 2d plane. Most 3d maps I've seen that try to take advantage of their 3d nature are a real pain to traverse and to grok at a glance without a lot of zooming and rotating.