Well, first of all I must admit I'm playing PES2008 only because I play online sometimes (very rarely in the last period to be honest), but I don't fell alright with it.
For the ones talking about next-gen: what do you mean for next-gen? A game that uses DX10? Well, PES2008 is NOT. PES2008 is developed upon DX9c.
Or do you mean a game that has proper lighting, proper 3d models and so on? Sorry, PES2008 is NOT next-gen either. And neither is FIFA08 PC.
So, if we want a "real" next-gen football game for PC, we have to wait at least until the end of this year.
Then, this is my personal list of the past PES games:
1) PES6.
The one still in use (along with PES2008) when we make multiplayer tournaments offline. I know shooting is a bit frustrating but hey, that's the way things go. Not always the ball goes where you imagined while shooting, and I ensure you can get plenty of great goals if you play a little and know how to shoot.
Regarding that Dudek goal posted in the other page: It COULD be scored also in real life, why not? Also Birindelli scored a goal like that, and Birindelli does NOT have good feet.
That's why I LOVE PES6.
2) PES4.
Personal opinion. Arcadey, too fast, but lovely afterall. I spent an entire summer playing it online and it was ACE. At least because it was the only one that had direct IP connection so if you knew the one you were playing against, you knew there would not have been lag.
3) PES5.
Probably the most balanced one, you were able to score a lot of great goals, but I found it just a little too easy. Quite every FK in the 16-25m range was a goal for me with Baseggio (Treviso) and it was somehow annoying.
So, if you want something to enjoy, just go for PES6 in my opinion.