Wario's second solo adventure brings some interesting changes to the series.
For this trip, Wario is invincible. And by that I mean death is not a gameplay mechanic. Everyone who plays this will win--or not win--w/o dying even once. The challenge here is not to avoid death but simply to get through the levels. The worst enemies can do is send Wario back to an earlier part of the stage but this provides sufficient motivation to play carefully w/o subjecting the gamer to the indignity of frequent reincarnation.
Overall, Wario Land II is not terribly hard and just playing straight through the main path of the game will take maybe a long afternoon for most gamers. However, Wario Land has significant extra content some of which takes considerably more skill to get through. In addition to the main storyline there is about an equal amount of extra levels found by locating secret doors in various other levels. Additionally, every level has two bonus games which must be completed to unlock an extremely challenging time attack mode which itself must be completed to get the best possible ending for the game. This works quite a lot like basically every Mario game since Super Mario World where there is a relatively easy way to simply finish the game but it set up in such a way that those who want it can find some really difficult challenges.
My one bone to pick as far as game play is in regards to some of the boss battles. Most of the bosses are relatively easy once you identify their patterns of attack and how to defeat them. Figuring this out though is a process of trail-and-error. This is fine in and of itself but since Wario cannot die, when a boss defeats him, he is sent to an earlier part in the level from which he must return back to boss in order to retry. This path back is generally pretty much free from hazard and just generally adds an extra thirty seconds of wandering around before the boss can be retried. This is adds absolutely nothing to challenge of defeating the bosses but simply adds a layer of frustration that I could have lived w/o.
Graphically, this is a pretty nice looking game for Game Boy Color. It looks like a later-era NES game, Super Mario Bros. 3, might be a good comparison. I personally though the original Wario Land had better, more-detail graphics--albeit in black and white--but these get the job done well enough. That said, I have always been a fan of the quirky, unique sounds that come out of the original Game Boy consoles and the music in Wario Land II turns that cheesy appeal all the way up and I find myself humming the tunes even days after playing.
Let us face it though, here in 2013, you are not playing a Game Boy Color game to admire its technical sophistication. You are either picking this up for nostalgia's sake or for sheer old-school platforming goodness. I am not so sure about the former but the latter is delivered here in spades and w/ an interesting twist to boot. I'd highly recommend picking up an original cartridge or downloading this from Nintendo' Virtual Console if you are looking for an interesting platformer w/ classic gaming appeal.