I don't really play my Diamond and Pearl much anymore. I'll take them out to battle over wifi, but most of what I do is on Shoddy. Don't get me wrong; I enjoy the games and love nearly everything about them, but when my main interest lies on the field of competitive battling, and I don't have wifi atm, I just don't find any reason to play on them other than training the occasional pokemon for a new team.
However, I still play my Silver and Emerald versions for fun, since I can't battle anyone on them.