c/p'd from an older thread
I can't really pick between the two, as I tend to prefer the other every second day. I came to realization that they're incomparable and I can't really exactly pick one to consider a favorite, not to mention I actually play them back to back (and this works really well, both of these games complement each other) so this makes it all the harder for me to choose, so I'll just say both.
As for the games themselves...there's not much beyond that I enjoy them. A lot. Wario Land 4 isn't even the best platformer, but it does things that I really wish more platformers did. There's something so offbeat and unique about it, and I can't stress the fact that there really isn't a single platformer like it, not even the other games in the series. What it excels at it does so well; this game has undeniably some of the best level design and use of item placement in any platformer. The levels are long, but they don't drag (coughyoshisislandcough) because they are paced exceptionally well and they are completely cohesive. Every thing in each stage complements each other so well, and leads to one another perfectly. But the thing about WL4 is about how everything placed in the design has a purpose. Enemies aren't just "there", they're either placed in a spot where they can be a hindrance to your progression, or even placed for you to USE them. This is the same for power ups. The game conveniently lets you use each power up or enemy to solve a puzzle or progress through the level. It's all about using what the games gives you to get the best possible outcome. Speedrunning? Top score? Everything is accounted for. WL4 also has collectibles that are required to beat the game. But here's the catch: The fun is in getting them, and they are hidden very well. When it comes to collectibles, most platformers either just make it hard to get, or obscure it completely with no hints. WL4 REWARDS the player with these collectibles just for searching through nooks and crannies.
There's really nothing wrong with Wario Land 4's design. Everyone can pick up and play it, because the level design and controls are pretty much flawless. It's just that not everyone can really appreciate it. It's so offbeat and strange, like I said before, that no one is really used to it. And that's fine, but on the other hand, I love what it achieves and consider its shortcomings to be negligible.
Warioware Inc isn't just a weird and offbeat game to a specific genre, it's insane in general. The fast paced action mixed with the zaniness of it really sets it apart. I mean, score attack based on how many consecutive wins you can get on 3 seconds minigame? How does that work? Well, Inc. does it SOMEHOW. When I typed that, I actually just wondered myself how the hell they managed to make something as ridiculously sounding as that so enormously fun and addictive. It's an achievement. The game is just a joy to play. Really. The only way I could tell someone why Warioware is good is saying it's "fun". I really don't need anything else, because it's true. On top of that, it's replayable, because the game throws so many stuff at you that even after years of playing you'll still be surprised and keep wanting to play more. While the later games in the series might be better (Twisted, in particular), Inc. is still this crazy concept in its purest form, and that's why it's my favorite.