Controls and graphics are better than WL1 (although the latter is hurt by being on Virtual Boy), but it's too short and becomes a slog for the final level and final boss
Wario Land II
Nice and fun 2D platformer with a lot of replayability with the multiple endings and alternate paths. The series really came into its own here.
Wario Land: Shake It!
Great level design, enemy design, and some fantastic aesthetics and music
Wario World
Fun little game with a great OST and is filled with personality but it's too short and is pretty rough around the edges
Wario Land: Super Mario Land 3
Follows the Mario formula a bit too closely but the power-ups are fun and the levels are all great
Wario Land 3
Cranks up the exploration by being a level-based metroidvania, and it works surprisingly well here and is a lot of fun, if a bit too long compared to the other games
Wario Land 4
Controls are better than Shake It and level design and enemy design are on-par, but the aesthetics and music aren't orgasm-inducing like Shake It. Still a really great game tho