Yes, all my gen 1-3 pokemon were caught between rse, frlf, colosseum, and gale of darkness or bred from those ones after evolving them for gen 4 dex entries so I could bring my entire living dex forward over the years. The most tedious jump is 3 to 4 because you can only transfer 6 every 24 hours(it doesn't reset when it hits midnight, it's at the time of transfer) per gba game(must be og fat ds or dslite models for the gba slot) and fucking with the clock blocks all daily stuff for 24 hours. Other than that the worst of it is needing two ds systems to get from 4 to 5 but a 3ds running the ds download play software should work. From there it's all done with bank, I don't know if they still do the free trial for new users but if they do and you wait until you're ready to actually do all your transfers you might be able to dodge the $5 subscription fee. If you'd like to bring pokemon from rbgy and gsc over directly to gen 7 you can do that with the 3ds eshop versions of the original games but I haven't bought those so you'd need to get the details from someone else.
