Released on the GBA, Wario Land 4 is an action platformer like the previous games and was the first proper GBA Wario game. In my Wario 3 review, I criticised a number of aspects of the game, mostly to do with the large confusing levels. Wario 4 Fixes many of the the problems I had mentioned of the Wario Land 3 game and is much closer to Wario Land 2 in terms of game design.
There are some very minor game design issues from my perspective:
Short game- Wario Land 2 had a huge number of short levels and alternative levels you can unlock depending on certain actions. Wario Land 4 on the other hand has very distinct levels but is extremey linear with only around 20 levels.
Lack of opportunities to use special abilities- For some reason, there are greatly reduced number of opportunities to use the special abilities/forms that Wario can transform into compared to other games. It's a bit of a shame really as that was often the most fun and unique parts of solving puzzles in previous Wario games.
Mini-games- Mini-games are okay but nothing to write home compared. You should probably just play Wario Ware instead.
Limited Lives- Wario now has hearts again and will have to replay the entire level if you lose them all. I think lives seem a bit like a step back from the precedent set by the previous games. The game was all about being invincible and being slowed down rather being forced to redo the entire game.
Wario Land 4 is a very fun game even today and a classic by my standards. It doesn't quite reach the standard that Wario Land 2 set but the fun levels, kooky graphics and solid gameplay makes it worth playing despite its age.