There was more to do in Spore's space stage than looking at planets. You could terraform them (which is quite relaxing and fun), populate plants, herbivores and carnivores, collect and genetically engineer life-forms, and turn them into sentient space-faring races, then try and build them up into an allied empire. All while building your own colonies and empire, exploring, going on trade routes, attacking enemy planets and stuff. Oh, and I recall there being some sort of tech tree and ship upgrades, plus you have the main quest to battle your way to the center of the galaxy, which is pretty challenging, especially on the hard difficulty.
There was also a cool feature, in that if you played a race in one game then started again, the kaiju on your starting world would be your race from the first time. I got my girlfriend at the time these plushy toy rotweiler pups, and based my first Spore creature on the toy. Then, started another game (on hardest difficulty), and had this gigantic killer doggie plushy trying to kill everything.
I don't know how that exactly compares to No Man's Sky, but there are plenty of things to do in Spore's space stage: unlike No Man's Sky, which uses seeds etc, you can completely rebuild the Spore galaxy almost any way you like.
The Ocean, Creature and Space stages were all pretty good. It's the middle stages which sucked: tribal and civilization stage. They just needed a better flow from Creature to Space. You basically want to take your time in Creature stage, spend a bit of time with Tribal, since it's kinda funny, speed right past Civilization stage (it's just a poor man's RTS) and spend a lot of time in Space. Also, it really helps if you go into the game with a clear concept for the race you want to create.