It's hard to believe that it's been almost ten years since I finished the first Pikmin game. I've actually been playing the sequel, Pikmin 2, off and on (mostly off) for what seems like forever (literally years). The gameplay is pretty much the same as the first, so you'd think that I would have gotten through it earlier than now. My main problem was that the first game had a rigid limit as to how many in-game days you could take to finish, whereas the sequel is completely open ended. Without any compelling goals in the sequel, I just didn't have any motivation to finish collecting the minimum amount of treasure required to "beat" the game and get to the credits, even though the gameplay was still generally enjoyable.
The sequel tweaks the structure of the original, and so instead of just exploring different outdoor areas, you also have a whole slew of caves to find and dive deep into. Caves do provide a nice change of pace, but there's really not a whole lot to them. There's no incentive or disadvantage to completing the multi-floor caves in one trip, so there's not much pressure. Again, this could be a good thing in general, but I just found that it made me not care much about being careful and planning ahead, and thus not care much about finishing the game.
The game is as cute as the first one, or even a little more so, and having a second character to control does provide some variety in terms of some simple puzzles and opportunities to be more efficient in accomplishing the various tasks the game presents. The game's mechanics are still very much just the "put key in lock" variety (i.e. use fire Pikmin on fire-breathing enemies, etc., etc.), but the challenge comes in trying to minimize the amount of game time spent, I suppose. As it was I just meandered through the game, admired the scenery, and didn't bother spending too much brainpower on it. Still a fun game, and I appreciated the generally relaxing ambience and all the humor in the descriptions of the treasures collected, but I definitely preferred the first one overall. I've actually already checked out Pikmin 3, so more on that before too long.