I do, though hardware can be an issue at times. Despite the improvements and new features over the years, there's something I still love about the first few generations (2 is my favorite, but I started with Red, and I love a lot of the gen 1 Pokémon). I regularly play gens 1 and 2 on my 3DS now, along with 7 and a bit of 6. I'll occasionally return to 3-5, though I've been playing them less of late. Not to mention all of the spinoffs.
I tend to return to a lot of older games, though, not just Pokémon. I would love to continue to see releases of older titles on newer hardware to make everything more accessible.