I've gone through so many keepers in my time on PES2 it's untrue. I'd hate to count how many points I've wasted. But I've narrowed them all down after testing to what I have found and in my opinion are the best 3 keepers.
1) Toldo (Not Free though)
2) Van Der Saar (Free)
3) Dida (Free)
All three are tall (always handy) to claim crosses etc and get down to those corners! I was particularly impressed with Toldo's handling. Van der Saar always seems to claw saves to safety away from oncoming strikers, and Dida is an all-rouner. Never tried Chilavert myself though. Me and a mate have a rivallry between our two teams and we're not allowed to have the same keeper (he has Chilavert). We always play 30 minute games (so many hours of my life!)
Here's the rerst of the people I've tried:
Peter Schmeichel - Gave away 2 penalties in first (& last) 3 games
Oliver Kahn - Twice. Shows that stats aren't always everything
Yashin - Bit short and DON'T let them shoot near post
Jennings - Same as above really
Cordoba - Not as good as stats suggest
Robinson - Parries too often, usually to attackers
Gilmar - Not as good as he was in PES1 (when he was king)
Buffon - Good, but makes unneeded dives
Maier - Bit short, German. Joking
Preud'Homme - Don't expect him to claim many crosses
I forget the rest