At this moment I'm in season 9, 2014/2015. These players have turned out really well after 9 seasons:
Name: Dennis Boskailo
Position(s): DRC
Note: Starts at Djurgarden and can be bought for €1.2M
Screenshot: 
Name: Georginio Wijnaldum
Position(s): AMRLC
Note: Starts at Feyenoord but in my game Liverpool bought him for €230K
Screenshot: 
Name: Género Zeefuik
Position(s): ST
Note: Starts at PSV but a friend of mine bought him with Feyenoord for a small price and in his 5th season with Feyenoord, Zeefuik scored
51 goals!!!
Screenshot: 
Name: Hao Junmin
Position(s): AMR
Note: Starts at Tiajin Shayu and in my game Coventry bought him (in the Championship) for €775K. He has played at Coventry for 7 seasons now and avr ratings are sweet!
Screenshot: 
Name: Adam McGurk
Position(s): AM/FC
Note: Starts at Aston Villa. In 2012/2013, Nottm Forrest bought him in the Premiership and in his first season he scored 18 goals and in his second season 15. They bought him for €1.6M. Not a bad price if I say myself...
Screenshot: 
I will check for more well-developed players and update the list!
Enjoy!
