Hardest and simultaneously funnest Pokemon game to challenge run?

[Mujar]

I cant really describe what im trying to ask well enough in the title so I'll explain more. I want to spice up the game a little bit fun and difficulty wise without restricting myself too hard (nuzlocke). The "challenge" if you can even call it that, is I wanna start with 6 Pokemon at level 3-5 and level them up fairly evenly throughout the game, start to finish, without ever actually grinding for any extended amount of time. Which game would you suggest I do this for? If you think that challenge alone would be enough to make the game substantially harder by itself then I'll probably play gen 1 or 2 since they're my favorite. Otherwise Ill play a gen you guys suggest. I know no Pokemon game is actually "hard" when you use everything to your advantage, (legendarys, grinding, shift battle phase, etc etc.) but I plan to keep it all to a minimum. So yea, whats your take on it?

 

[Puddle]

Gen II is probably one of the harder ones. Maybe Emerald due to the amount of game play and people like Flannery who have Pokemon with a move that can OHKO even if it's not very effective.

 

[Atomic Pirate]

Definitely Generation III. The Gym Leaders and Elite Four are all tough, as are the Champions (Both Steven and Wallace). Plus, there's a wide variety of Pokemon to raise.