I thought Spore was enjoyable the first time I played it. The second time was fine, but I can't see myself playing it much in the future.
The fundamental problem as I see it is that the game lacks depth in each of its stages while at the same time encompassing a great deal.
I'm not really interested in "realistic" evolution because I think I think it would be less fun than might be initially conceived. But I felt that there was a missed opportunity for adding real depth particularly for the creature stage.
One of the most disappointing factors is the complete lack of environmental impacts on the course of evolution. I would've had a number of different planetary factors such as gravity, atmosphere, temperature, ocean levels, etc. You could randomize these things or customize your own... This would impact the flora and fauna that would develop... If you're on a cold world or at least a cold latitude, you might want a furry coat instead of a body of slick scales (so in this case textures might actually be important if it's tied into that).
I also felt that they should've included some options for the things that you can't see... such as lungs vs. gills. Of course, to justify such a thing, you'd need an interesting water environment to go along with it, which I felt was also seriously lacking. It seems though that they plan to add that in future expansions.
I would've also liked to see the creatures more scalable. The ability to increase the creature's size (unless I missed something) seemed pretty limited without simply lengthening the limbs to make them taller. Size should increase the ability of the creature to reach different food sources, protect against predators (or if it is a predator increase it's lethality), but the downside should probably be a longer growth period and a greater demand for food for each level the creature is scaled up.
I also thought there could've been some interesting possibilities for nesting/homes and social organization. Every species has exactly the same kind of nest and they all lay eggs (they even lay exactly the same
kind of eggs). Nevermind the possibilities for aquatic homes, there could've been creatures that created burrows or nested in trees or on cliffs. Every species in the game uses small packs, but the level of social organization could've ranged from solitary creatures to large herds to bee or ant-like colonies with a rigid heirarchy. Each of these possibilities would come with their own strengths and weaknesses and would practical for animals depending on their food sources and size. A bee-like colony of elephant-sized creatures would probably have difficulty sustaining themselves for example.
Of course, I'm not looking for something that represents the full variety and specialization of nature because that wouldn't be possible. But I felt that for a game that allows you to create such varied creatures, they really don't have a variety of things to
do or much variation in how they behave. If you went for combat, you're directed along a narrow line of part choices, and then you pretty much just hack and slash your way to the tribal stage. If you decide to go for social/herbivore, you have an even narrower set of choices and then wash-rinse-repeat those silly little dances for other creatures. And if you pick omnivore, you essentially get the opportunity to not be particularly good at either of those two things. Which is kind of a metaphor for Spore itself which, while beautiful and moderately fun is neither a very good RPG nor a very good RTS.
I also felt that the game was rather stingy with the DNA points. I rarely had enough to make the creature I
wanted and instead had to settle on the one I could afford. (If I wanted to feel broke and powerless, I'd go outside!

) But if I worked harder to get more DNA points, I only hastened my passing to the next stage and thus I couldn't really get a chance to enjoy the fruits of my labor... And I felt it was a little silly that parts that served a purely aesthetic purpose cost valuable and indispensible DNA points.
I think that the "mating" factor for initiating the creature developer was an interesting and good idea. That gets a thumbs up, but as someone said already, I didn't like the fact that you could walk into it with one creature and walk out of it with something
completely different! I might suggest that instead of having DNA points affecting the total number of available parts, that instead you should accumulate points to determine how dramatically you can alter the creature from one evolution point to the next. It would not only make the game more realistic, it would make it more challenging as well. I felt that letting me jackknife from one strategy to another at will really made the game exceptionally easy. My choices really had no consequences because I could simply go back and overwrite them completely whenever I felt like it.
I won't get into the later stages too much because I think it's rather evident that they lack any real depth in spite of the great customability of the vehicles. Personally, I think if I were developing this game, I would've cut out the last three stages of the game and simply focused on the first two. I think one can reasonably say that it was excessive ambition with limited resources that killed this beast.