Lemmings simply offers something different. The sprites with flouncy hair soon become friends, their dedication and helplessness an irresistible pull. The size of the lemmings, that first impulse behind their creation, has the neat effect of making minor hills huge and half-screen gaps cavernous, thus ennobling their acts.
One of the best video games ever made. I still have it on all my computers just to explode some pixels while listening to MIDI classical music from time to time.