The heck with fairness. If you want to see your guests hunt some eggs then make the prize for second place the same as last place. There will be an egg hunting frenzy!
While not a good fit for all Easter parties, having a hunt with a sole winner works great when all(or almost all) of the egg hunters are close in age. It really raises the stakes and adds excitement. This is a great option for teens and tweens, but is not recommended younger kids and toddlers.
The Rules: Hide your eggs, give the kids their baskets and turn them loose. Whoever finds the most eggs is the sole winner and gets a big prize. You can give the other egg hunters a small participation prize, but the whole point of Winner Take All is that you have one big winner.
As a Secondary Egg Hunt: This game works very well as a secondary egg hunt, meaning a hunt to be held after your main egg hunt. The kids should already have a nice amount of loot and winning the secondary hunt would just be a bonus. Collect up all of the eggs from the previous hunt, making sure that any plastic eggs have the prize removed, and hide the eggs a second time. It is that simple, you are ready to go. You can even repeat the game as a third egg hunt if your guests are still wanting more and you have a prize left over.