Koizumi seems to be about the only one that had a lasting impression. Relatively young as you suggested and had charisma as well as trying to actually achieve stuff. I think it was the regular visits to Yasukuni that eventually did him in eventually though? Otherwise they seem to regularly rotate through mostly forgettable 70+ yr old LDP guys. They would usually fall foul of some corruption scandal, get replaced by a Mr 'Clean' who often turned out not quite so clean or was completely colourless and dull. The manga fan Aso was interesting - always seemed to have a sly smirk but also short lived.