Which is a little misleading -- because Datsyuk wasn't very well known.
I think Jarnkrok is coming over about at the same level as Filppula.
He is more well known because the continued internet age explosion in my opinion. In terms of accomplishments, I don't think Jarnkrok is far off where Datsyuk was back then, in fact he has a lead.
Filppula had not suited up for a single WC team, Jarnkrok has twice. Filppula had played two seasons of Mens league hockey in Sm-liiga, with one pretty strong season, Jarnkrok has played four with one pretty strong and two strong seasons. Jarnkrok was on a team that one the league Championship and he played a big role.
Datsyuk had played had played four seasons of RSL hockey before coming over, really only having one notably strong season, although he tore apart lower tier Russian leagues during one season in the middle of that stretch. He had made the WC team and started to create some buzz before coming over.
Realistically Jarnkrok is in front of both, but Datsyuk was a bigger deal coming over than Filppula. Based on European performances Jarnkrok has even been better. Of course a lot has changed over in Europe with the formation of the KHL.
Grigorenko and Zetterberg were a very big deal though in a lot of circles before ever making it across the pond though. On a whole different level than anybody else.