Many people compare Starbound to Terraria due to the fact that both of those games are 2D sandboxes, and I can see where they're coming from. However it's important to say that these games are fundamentally different even if we don't consider Starbound's space setting, still, to make things easier to understand I'll make some comparison:
- Story: Starbound has its main storyline, unlike Terraria which is just a survival boss rush, there's the first difference. The story in Starbound is actually pretty good considering how short most dialogues are, first you survive on a wild planet and then it turns out it's just the epilogue and now you're becoming the next avatar by uniting all races, so the story isn't the outstanding part about this game but I am still impressed, not gonna give any more spoilers, but I also must say there's some really deep lore if you read all of the books you get, I am not a lore master myself but I read some of it and there's stuff like past wars between these playable races and some really cool cataclysm stories.
- Customisation: as I mentioned about races, you have a choice between 7 races, each having its own gameplay bonuses, character reactions to different things, NPC reactions to your character, unique haircuts/outfits and so on. That's just the part with races, during your exploration you'll find A LOT of different clothes, accessories and weapons (I'll talk about them lower), Starbound has a lot of stuff, and so does Terraria, but from my experience the former has more of these things which may pique your interest, still, it's subjective and I don't want to count all items in both of these games. And the last, but not the least - furniture, Starbound has a huge freedom of choice in this department for builders, my FPS literally drops to 20 when I open the furniture catalogue to craft some of it, there's a lot of interior or exterior items and just decorative blocks, I am more than certain that there's more of it than in Terraria.
- Combat: it's surprisingly good, to return to the topic of weapons - there are 1 hand weapons, meaning you can hold 2 weapons at a time and use them by pressing your mouse buttons, and 2 hand weapons, all of them having special skills when you press the right mouse button, basically all melee weapons having combos of attacks instead of Terraria's repetitive single slashes, so fighting in Starbound felt pretty good. Boss battles are much more interactive since you don't have to spend an hour digging an arena to shoot Plantera from above, all bosses can only be met in main story domains where you can't build and you actually have to learn enemies' attack patterns and adapt to their styles, and indeed, all of them have different strategies of using your special skills.
- Progression: instead of 1 Hardmode world upgrade in Terraria, you actually find new ores on each planet type which is more dangerous than the last one, some of them having harsh conditions like being covered in water, being radioactive, having acid rains, being extremely cold or extremely hot or just straight up not having the atmosphere, you need to adapt to these conditions using special gadgets or consumables, and that's not to mention that some planets can only be found near specific stars, meaning you need more fuel, meaning more grind, that's how this game will try to slow you down. However, I had an issue with this progression - I had a very hard time trying to clear one of the story domains, so then I decided to spend a few hours mining on the highest level planet and came back to my ship to craft some stuff, and apparently crafted items are the strongest ones, there's also a division between melee, ranged and magic weapons but only in the very end of the crafting progression, similarly to the 4 pillars in Terraria (but I like this system more in Starbound because non melee armour isn't useless, while in Terraria your magic build helmet will literally have 5 times less defence than a melee one, considering the fact that basically all endgame melee weapons are ranged), then I returned back and all story domains became too easy to appreciate and enjoy them enough, I still loved it but now I understand the point of locking you from mining easily...
- Atmosphere: probably my favourite part about Starbound, sure, Terraria has some iconic colours and soundtracks, but this game just felt too gorgeous for a 2D sandbox. Backgrounds look very good and not repetitive at all, especially the toxic planet ones, they add a lot to the immersion. Structures always feel realistic no matter which style they represent. Textures and lighting somehow make it feel satisfying. Sound effects and OST just make it even more perfect, I unironically listen to some of these soundtracks outside of the game, they're really good in my opinion. There is a lot of wildlife and the random generation of hostile and passive mobs make the world more alive. Wherever you go you might encounter some big settlements where NPCs make some small movements instead of just randomly walking left or right and sitting on a chair at night. Your character's movements also make the gameplay more pleasing, since the character may have different idle stances back when you create them, and they always look differently if you crouch, walk, run, fight - you get what I mean. So, if I had to compare Starbound to Terraria in just a few words, it would probably be: "More casual, more atmosphere".
- Comfort: there's the casual part, after playing both of these 2D sandboxes I must say that Starbound has many comfortable parts which I would love to see in Terraria, for example - I hate putting walls in Terraria, they're bigger than normal blocks and they're hard to predict where you're even building with them, it's easy to miss a spot between walls because again - they're bigger than normal blocks but in reality you still need the same amount of them if it was just a normal block, and what I dislike even more is the fact that you always need a hammer when working with walls, you missclick - great, go take your hammer and then come back; in starbound it's very simple, background blocks are the same size as normal blocks and you're literally using the same blocks instead of crafting walls separately: LBM - put a physical block, RBM - put a background block, easy and casual, if you missclicked just take your manipulator which is an all-in-one tool: pickaxe, axe, hammer, flashlight, wire connector, liquid collector and even an inspector tool to see your character's reactions to different items, again, LBM - mine the physical block, RBM - mine the background block, THAT'S IT. There are many instances when you ask Terraria "Why?" and Starbound answers instead "We don't know why so here's the solution".
- Endgame: this situation is a bit tricky, first of all - yes, Terraria has more bosses and you could say that it has more endgame content. However it all depends on what you call the endgame, because Starbound has a lot of different features for you to do, their main issue is the lack of motivation to do any of it, for example catching random enemies to make them fight for you, since the generation of their bodies is very different it might take some time to find a creature you like visually; another example of these features is farming, there are many peculiar plants you can find on different types of planets, then you grow them and discover recipes to become the Gordon Ramsay of Starbound, I loved making some new unusual food with different effects, but it's not what all players want, and it alone is not enough to satisfy a person who likes cooking; in other words, Starbound has many ways to entertain its players but they're too different to call it all endgame. Mods can give you more content but sadly Starbound's community isn't nearly as big as Terraria's is, still, even with all of these problems this game has some big potential.
I will always love this gem of 2D games. 9.5/10