Obviously you should never just look at someone's stats, but at the player and person as a whole.
Afonso Alves was succesfull for just 1,5 seasons in Holland before he left to the EPL at age 27. During the short time in Holland there were plenty of vague issues surrounding him. He is of very low intelligence, he never went to any school and he only speaks Portuguese and even that not well, and he can't read. Does that sound like someone who will easily adapt and be succesfull in a top league in another country with all it's pressure etc? Not to me, it screams risk.
Kuyt, well, look at him. Look at any striker in the world that's been succesfull at the top. How many weren't very technically gifted and very precise? The only way a striker like Kuyt with his talents can be succesfull as a striker at the top is when he's really tall. Dutch football focusses more on the technical part, it's the dutch way. Kuyt with his physical strength, endurance and mentality was unmatched there. But the EPL is a much stronger and physical league which undermines Kuyt's talents more than in the dutch league.
And Babel, when he left Ajax he was still a talent, he hadn't even made it yet in the dutch league. He scored like 7 goals in his last season. Still, I think he does have the talent, just not the mentality.
That said though, people from every league fail in the EPL. Obviously when someone's succesfull at a good club in La Liga then he's more likely to succeed in the EPL too, but certainly not by definition.
There's still some players in the dutch league right now though who I believe could handle Liverpool level now or in the very near future:
Luis Suarez - S/SS/RW at Ajax
Stijn Schaars - DM/CM/LM at AZ
Sergio Romero - GK at AZ
Balázs Dzsudzsák - LW/LM at PSV
Ibrahim Afellay - AM/W at PSV
Being the most obvious ones I can come up with right now.
Like crouchino said though, if Keisuke plays like this consistently, then he certainly belongs in that list too in my opinion.
That said, dutch media reported today that Japanese investors are looking to buy him for Feyenoord.