Ugh, I can't choose because both side series interested me.
They both leave the mainstream RPG games, letting you have a taste of something different. I remember when the Mystery Dungeon Blue and Red Rescue Team were coming out, they promoted it with a commercial. "Wouldn't it be cool if you were a Pokemon?" Something along those lines. It was a long time ago, but I remember it almost as clearly. The kid was like "huh?" and I think it was a Pikachu that greeted him. XD Anyway, a world without humans training and capturing you was a good idea, and thanks to Chunsoft, it came alive.
The items on PMD games are hilarious, even though majority of them are from the main games. "X-Eye Seed", "Stun Seed" (that's hilarious to me for some reason), and the orbs. I'm still wondering how the game allows you have to so many Max Elixirs, but they're so hard to get in the main games. XD
Pokemon Ranger series just brought me to life. A game where humans aren't capturing Pokemon in Pokeballs for once. That, and they have so much better outfits than the main trainers. Even though they consist of the same colors, but who's worrying? That, and the starting heros/heroines aren't always ten years old, so that helped, too. The plots all made sense, and had me suspicious of characters that ended up being the bad guys. The lines said by the team (Go-Rock, Dim Sun and Nappers) were usually hilarious. The grunts, I mean. They would say something dumb before initiating the battle sequence.
I find the humor entertaining. The capturing of some Pokemon gets harder as it progresses, and the towns are all beautifully detailed. It appears every NPC in towns have somewhere to go, and that's what I like about it, too. Yeah, I definitely can't choose. XD