I spent a good portion of my life with SPORE and after all these years I'm still not bored and still open up new horizons. You have almost unlimited creativity that expands through several stages and if that's not enough for you then you'll be happy to know that there's a whole DLC giving you an opportunity to basically create your own "levels"/mini-games, being "Galactic Adventures". The GOG version is the best one to buy, considering it gives you a bugless (unlike Steam) client AND keys to go online, so if you're looking onto which version to buy you came to the right place.
