I know that this is going to sound like heresy, but there was a really good evolution based game on Facebook, and it was a Spore spinoff. I think it's gone now, but it was really cool. Especially if you had friends playing. You would all have creatures on one island, and you would give them different stats, and you would decide what they could and could not eat. And then you'd let them run around and one species was usually the best at surviving, and your friends would have to evolve their species to make them better and to compete with yours. It was a never ending cycle of constant evolution based on what you and your friends did.
Me and my friends made one island that was nothing but herbivores, and the one that was the best was the fastest, as they would run and get to the plants first and leave nothing for the other species. However, they had poor eyesight and couldn't see very far, so the one's with the better eyesight would live on by slowly making their way up to where the more plentiful food was in order to get some before the species with great eyesight managed to get there. I will admit that I cheated this island and after sixteen intervals of my species not surviving well enough, I turned it into a carnivore that had poor eyesight but could smell really well and was ferocious. Because the rest of my friends had never had a need to give their species any defenses, I quickly overcame them. The one's with good eyesight could see my creatures coming and would run away as quickly as possible if they say mine, so they could survive but not very well. The one with the speed could escape if they saw me first, but they never did as they had the terrible eyesight. To this day, my friends still refer to that island as "Your stupid carnivore that ruined paradise." But, hey. I made sure I won.
The name of the game was called Spore Islands, and after a brief search on Facebook, it is no longer there.