If you want a challenge, definitely try the new Pokemon Mystery Dungeon. Probably the most difficult game in the series.
I bought it and it's pretty bad. :/
Here's a few complaints I made on another website:
-The graphics are too saturated, I can't see anything
-The mini-map is pretty rubbish, I doesn't compensate for the graphics
-Your partner is a Naruto copy
-japanese school anime cliché (And I hate anime)
-controls are rubbish
-They still kept the dem 5 damage cap on the neutral attack (A)
-You start with too many moves (I mean, my Charmander tried to learn Ember, but it wasn't worth it because I had a better fire type move)
-The menu is confusing
-The sprites are not really great either, but it's better than the Charizard sprite in Blue/Red lol. Still not good
-I keep forgetting to press B when I back up, pushing my partner around, and it drains my belly. They could have reversed it, like press b to push.
And dude, just stack those oran berries and bring them everywhere, you'll fly through the game. They kinda changed the gameplay regarding the "difficulty" I'd say... in Rescue/Explorers, you could deal tons of damage, easily 2 hit ko any pokemon, but while you were powerful, you could get anihilated easily too. In this new one... well... I guess they kinda wanted to make it more like those main pokemon games battles or something. It takes ages to kill anything, same thing for them, and your moves keep missing. It's just so annoying, I want to reach the stairs geez. Also, pokemons seems to be less common to compensate. But well, just rack up on oran berries and you're fine, easy as that.