Platinum for me. It's still my fave game ever since it came out. The story was good, I played it over and over again. Sinnoh became my favorite region after I finished Platinum, and it's the only game where I felt compelled to do all the extra stuff I didn't have to. I've explained my love for Platinum version in a bunch of threads but yeah it's not just my fave gen 4 game, but my fave Pokemon game to date. HGSS is good, but even with all it's improvements it doesn't even touch Platinum version to me.
RIP anime version of Glovehead. Pokemon Adventures will save you.