As someone who's been with the series since the original, I gotta say I'm slowly starting to think that the 3rd one is my favorite of the bunch. I'm only 4 hours in, but as some veteran fans have already stated, I too feel like Pikmin 3 strikes the perfect balance between Pikmin 1 & 2. This game feels like the perfect evolution to the original Pikmin. This may sound weird to some people, but Pikmin 3 feels more like how Pikmin 2 should have been.
As you may have guessed, I didn't care too much for the second game. As much as I enjoyed myself with it, I felt like Pikmin 2 was overindulgence in ideas. It's almost like an "anything goes" kind-of-sequel. That game was just packed with content. The amount of collectables and treasures to collect in that game was insane. It basically became a dungeon crawler at one point too (the randomly generated caves, in my opinion, are unarguably awful). Although, if you think about it, it really was a brilliant marriage of gameplay and narrative. You need to collect treasure in order to "survive", but there's so much of it to unearth that you find yourself saying, "Just one more treasure..." and before you know it you've collected everything there is to find in the game. Without spoiling anything, what was cool and interesting was how a particular character basically shared the players sentiment and if you've played the game to the "real" ending, you know how that turned out for him (and you)...
For me though, Pikmin is all about the surface/world design. It's about those moments when you create a shortcut with a particular Pikmin type that allows you to access a boss/item/resource/area quicker. Pikmin 2 had those design philosophies, but the focus on randomly generated, underground cave "exploration" ruined it. It also completely went against the idea of having a time limit and allocating your resources and objectives during a day. When time froze underground there was no urgency, which I feel was a big part of the appeal to the original game. Again, Pikmin 3 hit a perfect balance with the new juice resource/system. It doesn't feel as tense as the original, but it's just enough to make you think about how to approach (or get enough out of) a day.
Just a few other things I LOVE about the 3rd game compared to the others. I can't believe how balanced the Pikmin types feel now. Reds can one shot small enemies when thrown from above. Also, the fact that your characters can't attack now means you have to rely completely on your Pikmin to deal damage. I thought it was a bit weird that Olimar and company could wipe out large monsters in the second game on their own. Having more definitive "weak" points now too is a god-send. Targeting body parts to stun/damage enemies more efficiently feels so perfect and natural with the Wii Remote. There's just so many small adjustments that a lot of newcomers probably don't even realize/notice that just elevate this game to the number one spot for me. It truly is the most refined entry in the series. I could probably talk about this game forever, but I'll just leave it at this for now.