The reason to own a Virtual Boy.
Basic gameplay involves around getting through the levels and jumping on anything that gets in your way. However, Wario has different caps that enable him to do lots of different stuff like shoot fireballs.
You use zippers to jump between the two virtual plains and it's actually quite a large part of the game. You'll need to fully explore the levels in order to find the hidden treasure.
The graphics are really nice in this game. The sprites are clear and crisp and the backgrounds are pretty detailed. You'll neverstrain your eyes in this game.
The sound is pretty great, too. Some really nice and dark tracks in places (Wario is a bad guy, after all) that really add atmosphere to the levels. I wouldn't say this is the best music I've heard in a game of this genre, but it does it's job well enough.
All in all, Wario Land is probably the best title on Nintendo's doomed system. It has everything you could want. Great graphics and sound coupled with good use of the system's 3D capabilities and good lastability. There's an insentive to play again. If you collect all the treasure you can unlock a harder version of the game with more monsters. If you have a VB, GET THIS GAME.