Although D/P are my least favorite games, I voted for FR/LG due to how the question is being asked.
D/P has some flaws which to me if they are fixed it could've been a very good Pokemon game (which most of them are fixed in Platinum), such as the slow battling and the limited Pokedex pre-Champion, but the games are really memorable for me: The Champion battle which is one of the most challenging battles for me (along with Lucian and in some ways the final battle against Cyrus), the awesome music, the interesting Poketch app, and more.
FR/LG to me is indeed better than D/P, but the problem is that there's really not much difference (like what Achromatic posted) compared with the originals. Yes, there's the held items, abilities, the Sevii Islands, the VS. Seeker and more, but other than that, FR/LG is not really much different compared with the originals for me. When I was doing a FR/LG run I found myself speedrunning the game and using the team which was almost the same as the one I had for the original, and it ended up being my shortest Pokemon main game run compared with the other games. After I beat it, even though it's great, it's less memorable compared with D/P and I don't mind skipping it for later.