Adventure + puzzle + Upgrade hunt= Awesome game.
Its so good that it made me play it over and over after 10 years, and I still like it.
That is because i love one thing of this game: The fact you cannot die!!!
It U turns the game experience know until that day, where you play until something kills you and sends you to the start or some "checkpoint", but Wario Land 3 flipped that fact making the enemies just an obstacle yo reach your goal, and even more amazing a TOOL to achieve that goal.
Who ever imagined that you must get hit by an enemy attack to make your way to the treasure?
I also loved the several endings to a single stage, which makes a reason to re-play a stage. Also the upgrade system is great because that makes you search treasure by treasure the item that will make you trough the way there.
Talking about the story I can say that it lacks a little of it. Its just: "Hey wario... Can you collect a little items for me because I am trapped here, but you can keep everything else you find". But at the end there's a big twist of the story, making the "good guy" being the Baddie and the bad guys just pretending to stop you from making a mistake. Although I disliked the final boss. Since it has a 1HKO attack its pretty easy and bizarre looking.
Talking about gameplay its awesome! I said earlier the fact that you cannot die, but the several enemy attacks that can help/damage you are just great, going from just an electric shock to becoming yourself a living fire ball. Also the secrets needs a lot of astuteness to be fulfilled making this game really hard if you want to complete it 100%.
The Graphics and sound are just right to the technology of that time too.
In resume:
Gameplay: 10
Graphics: 9
Sound: 9
Story: 8
Game Overall: 9