There's a thread
here about SF settings. This is about GAMES, which brings mechanics into it.
Traveller
Traveller is a popular go to, although the complaints about characters being fundamentally incompetent is right. Mechanically, it's a reliable 2d6 system, but in order to succeed at things 8 is the target number. Which means, without some kind of a bonus, you fail more than half the time. For things a character has skill in they'll get a bonus and it's not so much of a problem, but when they don't (which is more often than you would think) it can be a pain. Nothing a little handwavium won't fix though.
There are alien races, but they're mediocre in my opinion. The Aslan replacement for the Kzin of versions gone by is the strongest entry by far. The two "human" empires are extensive and expansive. The various frontiers and border areas provide a lot of room for Firefly style adventures with the opposing titan empires as part of the background. Which, if you ask me, is where the game is at it's best. As an aside it may be worth waiting for Marc Miller to release Traveller 5. I'm involved in an Ars Magica campaign (there's a thread about that elsewhere) while we wait.
Where Traveller excels is the long history of essentially backwards compatibility which means there is a TON of stuff available and the ship construction rules are really pretty good.
In truth, it's a strong all around package.
Hero
I'm not familiar with the Star Hero setting, but I'm a LONG time fan of the Champions/Hero games. And the mechanics are robust and you can do virtually anything you want. Pip and Flinx? Sure, the mechanics can model that. Lensmen? Sure. Dune? Yep. Problem is, if it's not the published system, you'll have to build it and that can be an overwhelming project.
Ships, vehicles - pretty much anything can be built. The vehicle combat rules are robust and not too difficult after one time through.
Others
Fading Suns comes to mind. The mechanics are good, the setting is grim, but makes more sense than 40K, but it has the same human-centric player posture as the 40k RPG line. It's also all but dead. That could be a deal breaker.
Cthulhu Tech: I love this one. We've got mechs, flying spaghetti monsters, aliens from beyond, violence aplenty. Cool mechanics (the poker inspired dice mechanics are fun and do make for some "game" in role playing game). Only one playable alien race, and they're about as alien as D&D elves. Single system, but there is a lot going on in it and there are plenty of hints and opportunities for things far beyond our little corner of the universe. While not quite Laser Pistols and Lovecraft it does kind of lean that way. I love it and highly recommend it. But I'd tell you Phoenix Command is cool too, just so you know.