To me it feels very obvious that Emerald was the best. Emerald was pretty much just the other games with a ton of stuff added! It had a allot of plot difference, the battle frontier was better by a long shot, added Safari Zone area, better gym puzzles, and best of all, the coolest trainer rematches. It also had the double battle system against two trainers at once.
I feel like this question is pointless. :P