It took a while to get a version of 'Pro Evo' on the PS2 (or International Superstar Soccer: Pro Evolution as it was known before then), but it was well worth the wait. Since then we've had a new version every year, with a steady improvement. Sadly, all good things come to an end, and while this may not be the last PES on the PS2, it shows that the end is nigh. Not that this is a bad game, it's just that the game has barely been improved over the previous version.
The cosmetic changes to the game are restricted to new data (which still has an enormous amount of licensed content missing), new commentators (John Champion and Mark Lawrenson – a reasonable improvement, but they still get repetitive rather quickly), and a new menu screen (yee haw!), but I don't think any of these actually improve over the previous game. Thankfully, where it matters, in-game, there have been some actual improvements. For a start, there isn't the slow down that blighted the previous two versions of the game. Secondly, there's a bigger gap between the good and the bad players – playing as England the ball flies around the midfield at an incredible pace whereas playing as Oman is a rather ponderous affair. Finally, the goalkeepers seem to have some new animations. The thing is though, I've played hundreds of games on PES6, and plenty already on PES2008 and while the game is still the best football game on any console (yes, this is better than the 360 and PS3 versions too) I don't think that anyone that already owns PES6 will want to pay full price for the new game.
Of course, if you're a regular player online you'd expect that you'd still want to upgrade, just because it'll be hard to find a PES6 game online soon. Actually, you may still want to hold onto your money – PES2008 across every single platform is atrocious online at the moment. You'll occasionally find a good game, but for the most part it's incredibly laggy online. I hope that the problem can be fixed with a server update in the near future, but it's pretty much unplayable for the time being.
If you don't have PES6 then you probably don't care about playing online and PES2008 is well worth getting. It's difficult to say for everyone that does own last year's game, and I've had to knock down the score accordingly. It's not bad, it's just that Konami hasn't really tried to move things on at all, and the fact that the PS2 is the least powerful platform out there isn't an excuse to avoid making any gameplay innovations.