A Modern Elite
Like Flatspace II, Jack of All Trades owes a lot to Elite, the pioneering space trading-and-combat game. You control a single starship, and as the game goes on, you can upgrade it from a tiny little trading craft with minor weapons to a large, powerful warship, or a large, fast cargo craft. And you have many options for what you want to do: trade and make big bux, become a bouty hunter, commit piracy on other traders, or get involved (and perhaps win) the ongoing interstellar war that (not incidentally) poses a risk to you if you stick with peaceful trading.
Starship as Hero
Starships Unlimited 3 has all the usual tropes of the 4X genre--a galaxy to explore, a deep tech tree, diplomacy with alien races--but with a major difference. The emphasis is, as the name suggests, on your starships. They're highly customizable, and the construction system makes each one you (or your opponents) build considerably more expensive than the last, so that even the largest civilization rarely has more than a dozen in play. This actually works to the game's advantage, because the starships become your protagonists, each individually interesting, and the missions they embark on have something of the feel of Star Trek to them, rather than being another mundane task in the long and (often) tedious grind of a typical 4X game.
You can think of Flatspace II as a sort of shmuppy Elite by way of NetHack. Like NetHack, the universe is randomly generated each time you start a new game; like shmups, starship combat is fast and intense; like Elite, you're a starship captain exploring a huge universe--and there are a whole slew of different roles you can take (trader, mercenary, bounty hunter, assassin, police officer, or scavenger).