I agree, some events just make the games more enjoyable, and to me, it makes them feel more complete. There's the Rotom forms in Platinum as you mentioned, and I think the Sinnoh map just feels a lot more complete when you have unlocked Newmoon Island, Seabreak Path and Flower Paradise.I've been doing the same thing for Gen IV and V games and it makes them feel so much more enjoyable to replay since you're really able to get the full experience, especially in Platinum where you can use all of Rotom's forms in-game. People have even set up GTS servers too which has been a lot of fun - I never got to use it back in the day so it's cool to be able to make full use of it now.
I didn't use the GTS a lot during the Gen 4 days (didn't have Wi-Fi during the first half of it, was burnt out on Pokémon during the second half) but I used it a lot in Gen 5. However, I don't have any real reason to use it nowadays since I have completed the Pokédex on all of my games and I have access to almost every Pokémon I need on my games. Still, it is really cool that it is up and running thanks to fans setting it up again after it was officially closed.
This would have been amazing. It might have been possible since there are many other things in B2/W2 which change or are added if you have used Memory Link, but I don't know.Part of me really wishes they'd made it so that if you used Memory Link and had performed the trade in BW, the Gigalith would have the OT and ID number of the BW player. But maybe that'd have been too difficult to program, idk.