Since talking about SC3 is actually more enjoyable than internet lawyering, I'll join in.
Star Control 3 is garbage.
As much as I want to leave the discussion at those words to prove the point, there are autists reading this that may sperg themselves to death because they can read text, but they can't read The Signs.
(Now you know how much fun can be had from internet lawyering.)
As Zombra mentions SC3 has some good points, like how some of the space races are memorable (the K'Tang, the Doog and the DakTakLakPak immediately spring to mind) and the Harika/Yorn society is interesting. But as Infinitron also mentioned the music is terrible (not even elevator muzak can be this bad), the writing of the non-Crux races is atrocious and that there's no game in there, besides the ship-to-ship combat... and even that is crap. (More on that later.)
Sadly it doesn't stop there. I'd like to say right now that I place no blame here at the feet of Legend Entertainment, they did the best they could with what they had... the least of which was time, from what I recall hearing. All the blame falls squarely on Accolade. Ironically Accolade made and released SC3 for the same reasons we're seeing the current legal tiff taking place - Toys for Bob held rights to Star Control that they shouldn't have according to industry norms at the time (where the publisher takes all and owns all) so steps had to be taken to remove TfB from the picture. First step: Make a Star Control game without them. Second step: Make a Star Control game without any content related to them. (That's what the aborted StarCon game from 1998 tried to do, among other things.)
Another problem is that Legend was being tasked to follow a tough act: Create a sequel to one of the greatest games of the past five years, a game that defies genres as well as expectations, widely praised and loved by almost everyone who's played it. It's like approaching Rush in 1977 and asking them to compose a follow-up album to Pink Floyd's Dark Side of the Moon.
SC3 has two casts of characters: Pre-established characters returning from SC2, and the new guys written by Legend. None of the old cast followed their established character traits from SC2, leaving the new guys to carry the game by themselves... and you know you're in for something when that line-up includes feudal space squids (with English accents), dumber-than-bricks dogmen and uppity fungus people.
In SC2 you start with an ill-equipped flagship that you can upgrade to your heart's content, making it suitable to your playstyle and situation. It can be a cargo hauler, deep space exploration vessel or a veritable gunboat that tears apart every other ship in the game, but losing it means Game Over, so it's a gamble. In SC3 you get a standardized 'pea-shooter' ship that is pants, forcing you to rely upon the other races to win the battles. It may seem like a minor shift, but it's a noticeable one: It means that if one considers SC2 to be a RPG* then SC3 most certainly isn't.
SC2 has you firmly in control of things - you are the Captain, you call the shots. Barring a few "We surrender"-choices you are free to make whatever choice you want and the game keeps on ticking. As the game is on a timer, the goal of the game is finding an optimal solution to the game, not the 'right' one. The timer also gives a sense of urgency and means that every choice has a consequence. Spend too much time gathering resources and you won't have time to do the main quest. Spend too little time and you're not ready to do it and will be playing catch-up.
SC3 has ICOM. ICOM tells you how you should play the game and removes control from you when you don't do as it says. If ICOM thinks you did something wrong, it's Game Over. This makes it infuriating to deal with the Owa, for example, as one wrong move there ends the game due to ICOM. There goes that feeling of significance. Unfortunately the game takes that theme a step further. Embedded in SC3 is a feeble attempt at a colony simulator. Every allied race has at least one colony that is supposed to be managed so that they contribute resources to your efforts. What it all boils down to is you building gas stations at (hopefully) strategic locations so that you don't get stranded in the ass-end of space somewhere... and even if you do manage that stupid feat, the game will happily wait for you while you spend years of in-game time building a colony in the nearest system and waiting for it to generate enough fuel to get you going again. So much for the urgency.
Then there are the bugs. In terms of bugs SC2 is virtually flawless. It takes effort to crash the game (in fact I've only ever seen that happen once). SC3 can strand you in Dead End-situations if you make as simple and innocent a choice as visiting some races in the wrong order. Go off the beaten path and the event script may not trigger, leaving you sitting there wondering what should be done next without a clue that you're hosed. At the same time there are a few events that are non-issues. A notable oddity in the SC3 line-up are the Ur-Quan, who made for terrific antagonists in SC2 but are not only allies in SC3, but sub-servient ones at that. Eager to serve, happy to assist. You nod and go along with it because you want their Dreadnoughts, so whatever. But if you build more Ur-Quan colonies than the original one, a sub-plot appears where the Ur-Quan rebel and half of their colonies "switch over" to become Kohr-Ah (uh-huh). This "quest" cannot be resolved, the Kohr-Ah will always be there to pester you. So how do you deal with this? You just don't build any Ur-Quan colonies. This is Bad Game Design 101, you don't spend time and effort implementing something into your game, then have the game inform the player that it's counter-productive to use it.
SC3 added 14 ships (IIRC) and the only fun ship in the entire line-up is the Harika/Yorn Ravager due to its unique game mechanics. At least half of the other ships added are mine-layers, and/or simply borrow elements from unused ships, leaving three ships that are different in any way. The Harika/Yorn ship treats crew like fuel (meaning it technically has three weapon systems) and has a strange but powerful main weapon, the Exquivan ship builds a wall around itself that it uses to block shots and ram enemies (and is single-handedly the most dickish ship to fight against in SC3, especially under computer control) and the Vyro-Ingo's ramming weapon sounds cool, but it doesn't even work all the time. Are the ships balanced? Fuck no, once I got my hand on the (upgraded) Doog ship I tore through every fight in the game with ease (save the last one, in which I used the Syreen instead) and in each of those fights I only used a single Doog ship, sitting quite still from where it warped in. That's how unbalanced the SC3 ships are.
Star Control 3 can console itself on one point: It's not a case of Betrayal! on a scale like Ultima 9 is, but it's still a kick in the teeth for those that loved Star Control 2, and utterly meaningless to everyone else. And it is garbage.
*About Star Control 2 being considered an RPG... what the fuck, RPG Codex? Have you lost your minds? At best the game has aspects of it, but SC2 purposefully defies genres. Get real.