The biggest problem with space-sims, IMHO, is exactly the same problem as was in way old school NES and SNES era RPGs. The pallette swap.
Now, I consider Freespace 2 the absolute god of space sims - but in essence, it really only has 4 (maybe 2) weapon types, of which 2 (maybe 1) are available to the player.
It has bolt-type weapons (blob cannons and every primarily a player has access to) which simply shoot a projectile straight. Missile type weapons, which are in essence bolt weapons which home in. Flak weapons, which are in essence bolt weapons which burst and do area affects at a certain range. And beam weapons, which even I can't catergorize as a version of bolt weapons.
Take you're average FPS. A pistol and a shotgun may be very similar, but in practice, they're used very differently. As is a sniper rifle and an SMG. Space sims in general, though, limit you to primaries (and even in freespace 2, all primaries are essentially the same weapon with slightly more damage when you hit, like an old school NES imp vs. Red Imp). They're more damaging versions of the same weapon which are used exactly the same way.
Same sims could learn a lot from Descent in this manner. The three way cannon didn't function like the gatling cannon - you had to adapt techniques to use the two of them. Three way was best close up, gatling made for excellent long range attacks because of it's essentially instant hit velocity - but you had to use control cause it knocked enemies around too. And the charge up plasma cannon behaved differently. Whatever weapon you had on, you altered your tactics to fit that weapon. FS2 - well, I'd rathed have kayser then a subach, but when you get right down to it, kayser or subach, I'm using exactly the same attack patterns and techniques to get it to hit.
Give me wave motion cannons, ballistic cannons that hit instantly but knock your enemy around. TIE-fighter style tractor beams. Make the mauler device from MOO2 a weapon, very very wide "No need to aim" but eats energy like a mofo and has a short range. Give me energy torpedos and missiles, weapons which travel in large conic sections, seekers, non-seekers, feignters, special purpose weapons. But make me THINK before I shoot. A kayser isn't a subach, and I shouldn't be able to say "Kayser, subach, Prometheus-S, Prometheus-R, they're all exactly the same". Give me spread guns and flamethrowers and laser and crush weapons and make me feel like my super laser isn't a palette swap of my stupid useless laser. And I'll buy your game.
But, then, if we're talking really far out. Give me that. Then let me dock with other ships, and take them over Buck Rogers: Countdown to doomsday style. In a pure FPS doom 3 game. Give me Mechwarrior: Mercs customizability but the living economy of X2: The threat. Let me get a combat mission at every space port if I want to, or make a fortune trading space-crack to aliens. Give me a deep plot, money AND a barter system, slave trading if I'm feeling real evil, research and development if I set up a base. Let me hire engineers to modify my weapons, and develop them to where they can use 14 different modules to make my laser to a super laser, but also let me hire researchers to create the new superweapon.
Give me a hot alien chick to romance and wierd aliens to talk with or blow up if I feel like. Let me disembark and explore alien ruins for schematics for the matter wave disruptor, mark 14, then let me trader if for 14 heavy lasers and a nubile young maiden.
Give me the best of Master of Orion 2, Doom 3, Freespace 2, Mechwarrior Mercenaries, Metroid Prime, Star Control 2 and Planescape:torment and I'll buy your game.
