Grand Melee is fun, but it works best when money is on the line, and since most players don't want to throw money down on a casual game....
Grand Melee is like poker, you can play it without betting, but it's kind of stupid. With money you just split the pot between the last man standing and the player who eliminated the most other players. What this does is encourage people to build deadly, aggressive decks that can survive the long haul, (because they want to get both halves of the pool), which in turn makes the game incredibly interesting because people are building fun combo-aggro-control decks so they can cover all their bases.