[T-Force]

I'm with hi19 and kommi on this in that I think Gen 3 was also the weakest generation but my issue stems from one other thing:
The lack of in-game time.

Generation 2 had that AWESOME feature where it could follow real time and go into night or day because of it. Gen 3 ditched that completely and I thought that's what really made Gen 2 stand apart (aside from the 16 gyms). While that feature was again brought back, that really crushed Gen 3 for me and is the reason I consider it the worst of the 6 generations.

That said, I might pick it up because a good chuck of the Pokémon I need for my X/Y Dex are Hoenn legends. Unless my girlfriend gets it, in which case, I'll ask her for them.