I've played the hell out of both the Pikmin games, and they definitely aren't easy.
The game's actually very little like real time strategy games, which I dislike... so I dunno what kind of game it is. The idea is this - you grow different Pikmin who all have different abilities. The goal in each game is to collect certain items that are too heavy for your main character to carry. So the Pikmin follow you around - up to 100. You use the little guys to fight, gather treasure, gather little pellets that grow new Pikmin, open gates, and do other little puzzle things. In a way, since you're controlling a hundred different little guys, it's like RTS, but since you control nearly all of them at once and everything's action based (you'll do a lot of Pikmin tossing), it's way more intense. I haven't ever played anything like it.
Pikmin 1 is a pretty short game (since you have a time limit to beat the game - which is not too limiting), but it's a lot cheaper than Pikmin 2. On the other hand, Pikmin 2 has no time limit and is more polished in every imaginable way.
I do like the games.