Remember the rather boring early-game grind of Terraria? Collecting ores for armor, getting boss items, and dying every so often got a bit stale before you finally unlocked the awesomeness that is hardmode, full of amazing enemies and items. Starbound is like the early game grind of Terraria the entire time, with nothing cool to look forward to. Tiered armor is boring- each set is incrementally better than the last, and that's it. Randomized weapons ensure that only a very small amount of them will be interesting- however, none of those randomly-generated weapons will be as interesting as weapons like the Golem's Fist in Terraria. The devs said they had a great story in the works, one for each faction, but that hasn't come through at all. Even the opening cutscenes for the races still aren't finished almost two years after release. I desperately wanted to enjoy this game, but it looks like I'll have to wait for Terraria Otherworld to satisfy my fighting/storying/building game itch.
Edit: I wrote some stuff in response to comments on my review, so I'll add them here.
First of all the game is not at all in an early stage of development. It's been a year and a half since the beta began, and the developers were aiming to release 1.0 last year: "We’re going to be releasing a stable update once the tech tree can be progressed through from start to finish, after that we’re going to be focusing on finishing up this todo list for 1.0. Which we are aiming for this year, but could go into next." from Tiyuri on September 19th. With that said, the game "should" be pretty close to done by now. We've had previews of the cutscenes from before the beta even came out. But whatever, story doesn't matter I guess.
The gameplay is just bad in almost every way. Weapons are bad. In Terraria, every non-tiered weapon is made
to be fun, so they're fun! In Starbound, they're created from an array of random parts. As far as I know, melee weapons have NOTHING to make them interesting- the only thing that matters about them is attack animation and DPS.
Armor is bad. Each tier is better than the last, but only from a numbers standpoint. In Terraria, the armor's set effects make it more of a personal preference- you actually have a choice between which armor you want, because they're actually different! What a novel idea. For example, on one run through I used meteorite armor for a good while into hard mode as a challenge, almost exclusively using my space gun, and it was damn fun. If you use a different armor in Starbound, you'll just die faster. Also the racial armor bonuses are pretty dull.
Building is bad. There's no real point to building anything other than decorating your ship since you need to hop planets pretty frequently. In Terraria, you have a reason to build houses (NPCs) and you even have more of a reason to decorate and care about your world because, well, it's the only world you have! Maybe colonization will help this a bit, but somehow I doubt it.
Mining is bad. There isn't anything cool or dangerous about it. There's stuff underground, sure, but the novelty of poop monsters, useless frog merchants, and ruins with no story behind them wears off pretty quickly. In Terraria, there are whopping great enchanted swords and pig monsters coming through walls trying to kill you, and treasure rooms, underground mini biomes with unique enemies and drops- it's quite a bit into hardmode that mining becomes farm-status without much to worry about. Even then, because you can actually make interesting items with the stuff you mine, Terraria still wins out.
Combat is bad. It's just really bad. Enemies have poor AI, are generally samey and boring (thanks again random generation!) and are weirdly balanced to either kill you in one or two hits or never even damage you even on the same world. There aren't any interesting drops either- meat, pixels, maybe a weapon, but that's it. Movement in combat is pretty boring, especially with the slow backwalking. The techs barely help in this respect because they're pretty clunky to use in combat.
Exploring is bad. Once you've seen one of something, you've seen all of them. There's not enough variety for a game which has exploration as one of its main selling points. I can think of maybe 12 types of big explorey things (avian temple, apex obstacle course, human prison colony, etc.) off the top of my head, and you'll probably find all of them within the first 10 or so hours of play.
Tech is the only interesting thing about the game, and even then it's because of their unrealized potential (which will probably remain unrealized in the future.) Accessories in Terraria have much cooler effects anyway.
So tell me, why would I recommend this game when Terraria does everything better?