If I had to choose between the Generation II games, then I would pick Crystal. I had Silver as my first 2nd Gen, and after playing through Crystal (which my brother gave to me), I experienced a much more exciting story than Silver. Crystal had a variety of new Pokemon (Gold exclusive Pokemon, to be more precise) which intrigued me the most. Another cool part was the introduction of Eusine. With him in the game, it brought more back-story to Suicune, as well as an easy catch for obtaining it. Crystal also brought in item retrievals from trainers on the cell. I really liked this feature, as I could get elemental stones and balls for free! Crystal is, hands down, my favorite Generation II game.