The FF9 characters looked like children for a reason... they *were* children (Zidane and Garnet were 16, IIRC... last I checked, adulthood was considered to be at 18)
All of the games have their pros and cons IMO, except FF7 which is all pro ;) (Not really, there's the poor graphics and poor translation)
I'd agree that FF9's end boss was the lamest fabrication of an end boss ever - but I found the story itself to be one of the best of the series.