In my experience, at the beginning of game it's between Casillas and Cech. Enyeama is the best VALUE keeper
IMO, but certainly knocking on the door of the best.
Long-term (not including regens) I find Vito Mannone from Arsenal gets a full call-up to the Italy squad when he's around 23-24 but unable to displace the regulars, and that's only if he gets a good deal of first team exposure. Have used him regularly at Leeds, but mainly as backup to Enyeama. Avg 8+ rating, though.
'Nuther good chap for the future is Geoffrey Jourdin. Available for <100k early on in the game and when I played as Chelski he replaced Cech when the bigheaded lump needed a new challenge about my 6th season in. Was France number one by the end of the season.