But Konami have used the same game engine since PES3, and you could even say it's older than that as they took the framework from their PS1 games

.
6 years of PES off the exact same base:
PES3
PES4
PES5
PES6
PES08
PES09
EA may have made more games on this generation, but that's only because they had the licenses for the World Cup, Euro Championships and Champions League. They have had the same amount of time with the console.
Your argument can also work against you, because with Konami having less games to produce, they can spend more time and effort on the ones they do make... I don't think they are done so much on trial and error either, and if they were, then Konami have never been good at that as some bugs have remained since the early editions of it, so what makes you think they can eradicate all the problems of 08 in a year when some of the bugs have been in the game for so many years?