Form follows function
Who's got time to prettify on that level?
Assuming you don't have some form of reentry force field and your ship needs to re-enter, your stuck with the simple geometrics Disk, Ball, Cylinder, Boomerang, or Dart.
What you use for propulsion also has a big influence, is it a big 1950's antigravity ring? (in which case your using a saucer or a ball) some big rocket nozzles? some sleek reaction less propulsion device (which under current physics you can't have anyway, but thats another story).
How radioactive is it? - does it need to be at the ned of a long spar to keep the crew from spitting out their teeth after a few weeks
Whats the ISP? - An engine that can do a brachistone trajectory is going to look seriously different to something that only fires off once every 6 months
Warships? Using lasers? in which case you want at least two of the dimensions minimised for dodging.
Using Missiles? Then it should be studded with counter missile kinetic weapons
At the end you can't just look at a spaceship and say "this looks real" or "this looks fake", you have to look at the spaceship in the context of the technology that built it. The USS Enterprise exists in a universe of cheap artificial gravity, field drives, energy reinforced structural components - so it makes sense in that context. However if the rest of the universe is babylon 5 (for example), then the USS enterprise is just wrong.