In the begining, there was Neopets. It was formerly a very entertaining pet RPG site, with a thriving message board known as the GC.
Then, TNP (The Neopets Team) got greedy, and everything began to slide downhill. Today, overcommercialization runs rampant, the games have become trite, and the GC is effectively dead.
Sensipets.com is seen by many as the reincarnation of the old spirit of Neopets. There, users will encounter a simple and engaging enviroment, as well as active and friendly message boards.
I consider the relationship between Neopets and Sensipets to be akin to Internet Explorer and Firefox (Mozilla).