I suppose I will not proceed after finishing the evolution process (maybe just another play as an aggressive race).
Space stage is by far the most complete part of the game... everything else is just the build up.
At the end of the day - the appeal to Spore is all about one's own creativity and style. Like playing with legos... it's a medium through which you can create props and play out your own imagination...
If you have the complete collection... I guess that means you have Galactic Adventures?
Spore Galactic Adventures and it's scope for creativity is what inspired Microsoft to create Project Spark...
But I have some news for you... the included adventures are pretty dry and dull... you will need to acquire community made adventures to really experience what GA has to offer... also, if you are only playing with the default creations... then you are really missing out... there are some AMAZING creations out there... creatures you will not believe are possible to make with the Spore engine... some truly mind-blowing things.
THAT's what Spore was... you're exploring space and you see... what!!??? WHAT is that? OMG!!! Who made that thing? How did they...? Then you go and have a look at what else they've made...
.... then you are so inspired you try your hand making something similar....
... sometime later, you realize you're an addict... can't stop making PRETTY MONSTERS!!!!!
If you are offline, or have no account, or the servers are down... you can always download creations straight from the web-based Sporepedia
http://www.spore.com/sporepedia
Just right-click the picture of any creation and download the .png ... then you can either find your creations folder (usually in your documents folder) on your hard drive and drop them in there, or you can run Spore in windowed mode and drag-drop them all straight into your Sporepedia.
Getting GA Adventures is a little more tricky. You will need Chrome installed, and you will need to download and install the extension described here:
Here it is:
https://dl.dropboxusercontent.com/u/40354246/sporepediaDownloader2.crx
put all the files in a folder. Then, in chrome under extensions, turn on developer mode and then 'load unpacked extension' - navigate to the folder and there you should have it.
The little icon at the top right will turn green when you are in a valid part of the sporepedia and you just click it and it will batch-download every included creation in the adventure you are looking at.
I suggest you set this up to download to a specific folder, and create another folder with the name of the adventure you are viewing. When the download is complete (it will be quick), move all the files from the download folder into the named folder... then repeat the process for the next adventure you are interested in.
Then you can drag-drop those adventure files into your Sporepedia the same way you do stand alone creations.
You will need to keep that extension folder handy, as you may have to reinstall it every time you use Chrome.
There are a bewildering number of adventures out there... a huge amount of them not worth your time... so this is a good place to start:
http://www.spore.com/sporepedia#qry=ssc-500453354296
This is a pretty good collection of some of the best adventures you will find.
Have fun!