Frontier...
The fact they used realistic space physics is amazing, so many other games even of this era have spacecraft operate in the same way as aircraft do. Like wise it was one of the first sandbox games out there which just let you do whatever you want.
If it wasn't for a static and easily exploited economical system and a very basic combat system it would be a lot better. When you can run luxury goods from earth to van man star and even if caught smuggling still sell off your cargo for a massive profit again, and again, and again... well. Economy becomes useless then.
Oh and combat... you have lasers, lasers and partial weapons that act like... yep... lasers.
IF someone was to take the premise, add in the graphic updates seen these days and put a more fluid system of politics, economy and the likes it would be a great game. Particularly if you let the player get rich and powerful in trade and move on to world domination and eventually becoming a political power in their own right.
Hell no story line, the original never had one, and I lost weeks playing that game.