I own the last gen games (X and Sapphire I think) but I think I have the most fun dicking around with romhacks and randomizers for the older generations.
The amount of replayability that randomizers add is simply terrifying.
What's Randomizer and how does it work? I finished playing Soul Silver several weeks ago for the second time, I think I'm going to revisit the 4th generation now, my fav version from Sinnoh is definitely Platinum.