Quoted By:
V* > IV* > VI > III > II > I (with none of them actually being bad)
I love Gen I for starting the franchise and for having amazing glitches and weird mechanics, but everything past it is a better game by any sensible measure.
*Gens V and IV I consider superior largely by virtue of their late installments like Platinum, HG/SS, and BW2. These games still boast the most complete and expansive post-game content in the series, with BW2 being the best of these. Diamond and Pearl had significant problems and Black and White, while better, felt kind of incomplete.